Parallax Propeller Owner's manual

Propeller Manual

Version 1.2

WARRANTY

Parallax Inc., dba Parallax Semiconductor, warrants its products against defects in materials and workmanship for a period of 90

days from receipt of product. If you discover a defect, Parallax Inc. will, at its option, repair or replace the merchandise, or

refund the purchase price. Before returning the product to Parallax, call for a Return Merchandise Authorization (RMA)

number. Write the RMA number on the outside of the box used to return the merchandise to Parallax. Please enclose the

following along with the returned merchandise: your name, telephone number, shipping address, and a description of the

problem. Parallax will return your product or its replacement using the same shipping method used to ship the product to

Parallax.

14-DAY MONEY BACK GUARANTEE

If, within 14 days of having received your product, you find that it does not suit your needs, you may return it for a full refund.

Parallax Inc. will refund the purchase price of the product, excluding shipping/handling costs. This guarantee is void if the

product has been altered or damaged. See the Warranty section above for instructions on returning a product to Parallax Inc.

COPYRIGHTS AND TRADEMARKS

printed copy of this documentation or software you agree that it is to be used exclusively with Parallax products. Any other uses

are not permitted and may represent a violation of Parallax copyrights, legally punishable according to Federal copyright or

intellectual property laws. Any duplication of this documentation for commercial uses is expressly prohibited by Parallax Inc.

Duplication for educational use is permitted, subject to the following Conditions of Duplication: Parallax Inc. grants the user a

conditional right to download, duplicate, and distribute this text without Parallax's permission. This right is based on the

following conditions: the text, or any portion thereof, may not be duplicated for commercial use; it may be duplicated only for

educational purposes when used solely in conjunction with Parallax products, and the user may recover from the student only the

cost of duplication.

This text is available in printed format from Parallax Inc. Because we print the text in volume, the consumer price is often less

than typical retail duplication charges.

Parallax, Propeller Spin, and the Parallax and Propeller Hat logos are trademarks of Parallax Inc. BASIC Stamp, Stamps in

Class, Boe-Bot, SumoBot, Toddler, and SX-Key are registered trademarks of Parallax, Inc. If you decide to use any trademarks

of Parallax Inc. on your web page or in printed material, you must state that (trademark) is a (registered) trademark of Parallax

Inc.” upon the first appearance of the trademark name in each printed document or web page. Other brand and product names

herein are trademarks or registered trademarks of their respective holders.

ISBN 9781928982593

1.2.0-11.06.14-CWR

DISCLAIMER OF LIABILITY

Parallax, Inc., dba Parallax Semiconductor, makes no warranty, representation or guarantee regarding the suitability of its

products for any particular purpose, nor does Parallax, Inc., dba Parallax Semiconductor, assume any liability arising out of the

application or use of any product, and specifically disclaims any and all liability, including without limitation consequential or

incidental damages even if Parallax, Inc., dba Parallax Semiconductor, has been advised of the possibility of such damages.

INTERNET DISCUSSION LISTS

We maintain active web-based discussion forums for people interested in Parallax Propeller products. These forums are

accessible at forums.parallax.com:

 Propeller chip – For all customers using Propeller chips and products.

 Parallax Semicondutor – For commercial product developers who use Propeller chips.

 BASIC Stamp – This list is widely utilized by engineers, hobbyists and students who share their BASIC Stamp

projects and ask questions.

 Stamps in Class® – Created for educators and students, subscribers discuss the use of the Stamps in Class series

of tutorials in their courses. The list provides an opportunity for both students and educators to ask questions

and get answers.

 HYDRA – for enthusiasts of the Propeller-powered HYDRA videogame development system.

 Parallax Educators – A private forum exclusively for educators and those who contribute to the development of

Stamps in Class. Parallax created this group to obtain feedback on our curricula and to provide a place for

educators to develop and obtain Teacher’s Guides.

 Robotics – Designed for Parallax robots, this forum is intended to be an open dialogue for robotics enthusiasts.

Topics include assembly, source code, expansion, and manual updates. The Boe-Bot®, Toddler®, SumoBot®,

HexCrawler and QuadCrawler robots are discussed here.

 SX Microcontrollers and SX-Key – Discussion of programming the SX microcontroller with Parallax assembly

language SX – Key® tools and 3rd party BASIC and C compilers.

 Javelin Stamp – Discussion of application and design using the Javelin Stamp, a Parallax module that is

programmed using a subset of Sun Microsystems’ Java® programming language.

ERRATA

While great effort is made to assure the accuracy of our texts, errors may still exist. If you find an error, please let us know by

sending an email to editor@parallax.com. We continually strive to improve all of our educational materials and documentation,

and frequently revise our texts. Occasionally, an errata sheet with a list of known errors and corrections for a given text will be

posted to our web site, www.parallax.com. Please check the individual product page’s free downloads for an errata file.

SUPPORTED HARDWARE AND FIRMWARE

This manual is valid with the following hardware and firmware versions:

Hardware Firmware

P8X32A-D40

P8X32A-Q44

P8X32A-M44

P8X32A v1.0

CREDITS

Authorship: Jeff Martin. Format & Editing, Stephanie Lindsay.

Cover Art: Jen Jacobs; Technical Graphics: Rich Allred; with many thanks to everyone at Parallax Inc.

Table of Contents 
PREFACE ............................................................................................................................... 11 
CHAPTER 1 : INTRODUCING THE PROPELLER CHIP....................................................... 13 
CONCEPT ............................................................................................................................. 13 
PACKAGE TYPES ................................................................................................................... 14 
PIN DESCRIPTIONS................................................................................................................ 15 
SPECIFICATIONS ................................................................................................................... 16 
HARDWARE CONNECTIONS .................................................................................................... 17 
BOOT UP PROCEDURE .......................................................................................................... 18 
RUN-TIME PROCEDURE ......................................................................................................... 18 
SHUTDOWN PROCEDURE....................................................................................................... 19 
BLOCK DIAGRAM ................................................................................................................... 20 
SHARED RESOURCES............................................................................................................ 22 
SYSTEM CLOCK .................................................................................................................... 22 
COGS (PROCESSORS) ........................................................................................................... 22 
HUB ..................................................................................................................................... 24 
I/O PINS ............................................................................................................................... 26 
SYSTEM COUNTER ................................................................................................................ 27 
CLK REGISTER ..................................................................................................................... 28 
LOCKS .................................................................................................................................. 30 
MAIN MEMORY...................................................................................................................... 30 
MAIN RAM ........................................................................................................................... 31 
MAIN ROM........................................................................................................................... 32 
CHARACTER DEFINITIONS ...................................................................................................... 32 
LOG AND ANTI-LOG TABLES................................................................................................... 34 
SINE TABLE .......................................................................................................................... 34 
BOOT LOADER AND SPIN INTERPRETER.................................................................................. 34 
CHAPTER 2 : SPIN LANGUAGE REFERENCE .................................................................... 35 
STRUCTURE OF PROPELLER OBJECTS/SPIN ........................................................................... 36 
CATEGORICAL LISTING OF PROPELLER SPIN LANGUAGE ......................................................... 38 
Block Designators........................................................................................................... 38 
Configuration .................................................................................................................. 38 
Cog Control .................................................................................................................... 39 
Process Control.............................................................................................................. 39 
Flow Control ................................................................................................................... 39 
Memory........................................................................................................................... 40 
Directives........................................................................................................................ 41 
Registers ........................................................................................................................ 41 
Constants .......................................................................................................................42 
Variable .......................................................................................................................... 42 
Unary Operators............................................................................................................. 42 
Binary Operators ............................................................................................................ 43 
Propeller Manual v1.2 ·  Page 5 

Table of Contents

Syntax Symbols ..............................................................................................................44

SPIN LANGUAGE ELEMENTS ...................................................................................................45

Symbol Rules..................................................................................................................45

Value Representations....................................................................................................45

Syntax Definitions ...........................................................................................................46

ABORT....................................................................................................................................47

BYTE .....................................................................................................................................51

BYTEFILL ..............................................................................................................................57

BYTEMOVE ..............................................................................................................................58

CASE .....................................................................................................................................59

CHIPVER ................................................................................................................................62

CLKFREQ ................................................................................................................................63

_CLKFREQ ..............................................................................................................................65

CLKMODE ................................................................................................................................67

_CLKMODE ..............................................................................................................................68

CLKSET..................................................................................................................................71

CNT .......................................................................................................................................73

COGID....................................................................................................................................75

COGINIT ................................................................................................................................76

COGNEW..................................................................................................................................78

COGSTOP ................................................................................................................................83

CON .......................................................................................................................................84

CONSTANT ..............................................................................................................................91

CONSTANTS (PRE-DEFINED) ...................................................................................................93

CTRA, CTRB...........................................................................................................................95

DAT .......................................................................................................................................99

DIRA, DIRB.........................................................................................................................104

FILE ...................................................................................................................................107

FLOAT..................................................................................................................................108

_FREE..................................................................................................................................110

FRQA, FRQB.........................................................................................................................111

IF .......................................................................................................................................112

IFNOT..................................................................................................................................117

INA, INB ............................................................................................................................118

LOCKCLR ..............................................................................................................................120

LOCKNEW ..............................................................................................................................122

LOCKRET ..............................................................................................................................125

LOCKSET ..............................................................................................................................126

LONG ...................................................................................................................................128

LONGFILL ............................................................................................................................134

LONGMOVE ............................................................................................................................135

LOOKDOWN, LOOKDOWNZ.........................................................................................................136

LOOKUP, LOOKUPZ................................................................................................................138

Page 6 · Propeller Manual v1.2

Table of Contents

NEXT................................................................................................................................... 140

OBJ..................................................................................................................................... 141

OPERATORS ....................................................................................................................... 143

OUTA, OUTB ........................................................................................................................ 175

PAR..................................................................................................................................... 178

PHSA, PHSB ........................................................................................................................ 180

PRI..................................................................................................................................... 181

PUB..................................................................................................................................... 182

QUIT................................................................................................................................... 186

REBOOT ............................................................................................................................... 187

REPEAT ............................................................................................................................... 188

RESULT ............................................................................................................................... 194

RETURN ............................................................................................................................... 196

ROUND ................................................................................................................................. 198

SPR..................................................................................................................................... 200

_STACK ............................................................................................................................... 202

STRCOMP ............................................................................................................................. 203

STRING ............................................................................................................................... 205

STRSIZE ............................................................................................................................. 206

SYMBOLS............................................................................................................................ 207

TRUNC ................................................................................................................................. 209

VAR..................................................................................................................................... 210

VCFG................................................................................................................................... 213

VSCL................................................................................................................................... 216

WAITCNT ............................................................................................................................. 218

WAITPEQ ............................................................................................................................. 222

WAITPNE ............................................................................................................................. 224

WAITVID ............................................................................................................................. 225

WORD................................................................................................................................... 227

WORDFILL............................................................................................................................ 234

WORDMOVE............................................................................................................................ 235

_XINFREQ............................................................................................................................ 236

CHAPTER 3 : ASSEMBLY LANGUAGE REFERENCE ....................................................... 238

THE STRUCTURE OF PROPELLER ASSEMBLY ........................................................................ 238

Cog Memory ................................................................................................................. 240

Where Does an Instruction Get Its Data? .................................................................... 240

Don't Forget the Literal Indicator '#'.............................................................................. 241

Literals Must Fit in 9 Bits .............................................................................................. 241

Global and Local Labels............................................................................................... 242

CATEGORICAL LISTING OF PROPELLER ASSEMBLY LANGUAGE............................................... 243

Directives...................................................................................................................... 243

Configuration ................................................................................................................ 243

Propeller Manual v1.2 · Page 7

Table of Contents

Cog Control...................................................................................................................243

Process Control ............................................................................................................243

Conditions .....................................................................................................................243

Flow Control..................................................................................................................245

Effects ...........................................................................................................................245

Main Memory Access....................................................................................................245

Common Operations.....................................................................................................245

Constants......................................................................................................................247

Registers.......................................................................................................................248

Unary Operators ...........................................................................................................248

Binary Operators...........................................................................................................249

ASSEMBLY LANGUAGE ELEMENTS ........................................................................................250

Syntax Definitions .........................................................................................................250

Opcodes and Opcode Tables .......................................................................................251

Concise Truth Tables....................................................................................................252

Propeller Assembly Instruction Master Table ...............................................................253

ABS .....................................................................................................................................257

ABSNEG................................................................................................................................258

ADD .....................................................................................................................................259

ADDABS................................................................................................................................260

ADDS ...................................................................................................................................261

ADDSX..................................................................................................................................262

ADDX ...................................................................................................................................264

AND .....................................................................................................................................266

ANDN ...................................................................................................................................267

CALL ...................................................................................................................................268

CLKSET................................................................................................................................271

CMP .....................................................................................................................................272

CMPS ...................................................................................................................................274

CMPSUB................................................................................................................................276

CMPSX..................................................................................................................................277

CMPX ...................................................................................................................................280

CNT .....................................................................................................................................282

COGID..................................................................................................................................283

COGINIT ..............................................................................................................................284

COGSTOP ..............................................................................................................................286

CONDITIONS ( IF_X ) ............................................................................................................287

CTRA, CTRB.........................................................................................................................288

DIRA, DIRB.........................................................................................................................289

DJNZ ...................................................................................................................................290

EFFECTS ( WC, WZ, WR, NR ) ....................................................................................................291

FIT .....................................................................................................................................292

FRQA, FRQB.........................................................................................................................293

Page 8 · Propeller Manual v1.2

Table of Contents

HUBOP ................................................................................................................................. 294

IF_X (CONDITIONS)............................................................................................................. 295

INA, INB ............................................................................................................................ 297

JMP..................................................................................................................................... 298

JMPRET ............................................................................................................................... 300

LOCKCLR ............................................................................................................................. 303

LOCKNEW ............................................................................................................................. 304

LOCKRET ............................................................................................................................. 305

LOCKSET ............................................................................................................................. 306

MAX..................................................................................................................................... 307

MAXS................................................................................................................................... 308

MIN..................................................................................................................................... 309

MINS................................................................................................................................... 310

MOV..................................................................................................................................... 311

MOVD................................................................................................................................... 312

MOVI................................................................................................................................... 313

MOVS................................................................................................................................... 314

MUXC................................................................................................................................... 315

MUXNC ................................................................................................................................. 316

MUXNZ ................................................................................................................................. 317

MUXZ................................................................................................................................... 318

NEG..................................................................................................................................... 319

NEGC................................................................................................................................... 320

NEGNC ................................................................................................................................. 321

NEGNZ ................................................................................................................................. 322

NEGZ................................................................................................................................... 323

NOP..................................................................................................................................... 324

NR ...................................................................................................................................... 325

OPERATORS ....................................................................................................................... 326

OR ...................................................................................................................................... 327

ORG..................................................................................................................................... 328

OUTA, OUTB ........................................................................................................................ 330

PAR..................................................................................................................................... 331

PHSA, PHSB ........................................................................................................................ 332

RCL..................................................................................................................................... 333

RCR..................................................................................................................................... 334

RDBYTE ............................................................................................................................... 335

RDLONG ............................................................................................................................... 336

RDWORD ............................................................................................................................... 337

REGISTERS......................................................................................................................... 338

RES..................................................................................................................................... 339

RET..................................................................................................................................... 342

REV..................................................................................................................................... 343

Propeller Manual v1.2 · Page 9

Table of Contents

Page 10 · Propeller Manual v1.2

ROL .....................................................................................................................................344

ROR .....................................................................................................................................345

SAR .....................................................................................................................................346

SHL .....................................................................................................................................347

SHR .....................................................................................................................................348

SUB .....................................................................................................................................349

SUBABS................................................................................................................................350

SUBS ...................................................................................................................................351

SUBSX..................................................................................................................................352

SUBX ...................................................................................................................................354

SUMC ...................................................................................................................................356

SUMNC..................................................................................................................................357

SUMNZ..................................................................................................................................358

SUMZ ...................................................................................................................................359

SYMBOLS ............................................................................................................................360

TEST ...................................................................................................................................362

TESTN..................................................................................................................................363

TJNZ ...................................................................................................................................364

TJZ .....................................................................................................................................365

VCFG ...................................................................................................................................366

VSCL ...................................................................................................................................367

WAITCNT ..............................................................................................................................368

WAITPEQ ..............................................................................................................................369

WAITPNE ..............................................................................................................................370

WAITVID ..............................................................................................................................371

WC .......................................................................................................................................372

WR .......................................................................................................................................373

WRBYTE................................................................................................................................374

WRLONG................................................................................................................................375

WRWORD................................................................................................................................376

WZ .......................................................................................................................................377

XOR .....................................................................................................................................378

APPENDIX A: RESERVED WORD LIST ..............................................................................379

APPENDIX B: MATH SAMPLES AND FUNCTION TABLES.................................................380

INDEX....................................................................................................................................386

Preface

Thank you for purchasing a Propeller chip. You will be spinning your own programs in no

time!

Propeller chips are incredibly capable multiprocessor microcontrollers; the much-anticipated

result of over eight years of the intense efforts of Chip Gracey and the entire Parallax

Engineering Team.

This book is intended to be a reference guide to Propeller chips and their native programming

languages, Spin and Propeller Assembly. For a programming tutorial and Propeller Tool

details, please refer to the on-line help that is installed with the Propeller Tool software.

Have fun!

Despite our best efforts, there are bound to be questions unanswered by this manual alone.

Check out our Propeller chip discussion forum – (accessible from www.parallax.com via the

Support → Discussion Forums menu) – this is a group especially for Propeller users where

you can post your questions or review discussions that may have already answered yours.

In addition to the forum, visit the Propeller Object Exchange (obex.parallax.com) for free

access to hundreds of Propeller objects made by customers and Parallax Engineers. Besides

being immediately useful for your own applications, Propeller objects written by various

authors are a great resource for studying techniques and tricks employed by the very active

Propeller community.

Editor’s Note: About Version 1.2

The changes to this version focus on corrections and small additions to clarify certain

sections. The PDF version of this document highlights each technical change.

In addition, a complete list of technical content changes between Version 1.1 and Version 1.2

can be found in the Propeller Manual Supplement & Errata. The pagination between these

two versions has not changed, so the page numbers cited refer to both versions.

The most significant technical corrections relate to the number of clock cycles required by

certain Propeller Assembly instructions. These include all hub instructions as well as WAITCNT,

p. 368, WAITPEQ, p. 369, WAITPNE, p. 370, and WAITVID, p. 371. These changes are reflected in

each instruction’s Opcode Table, as well as in the the Propeller Assembly Instruction Master

Table and its notes, p. 253. For complete details, revised illustrations, and a list of hub

instructions, see the Hub section, p. 24.

Propeller Manual v1.2 · Page 11

Preface

Page 12 · Propeller Manual v1.2

Other notable changes include:

 A clarification about RAM/ROM organization in Table 1-2: Specifications, p. 16.

 An expanded explanation of Locks, page 30.

 A correction to the XTAL3 external crystal range in the Table 2-3: Clock Mode Setting

Constants, p. 68.

 A new section titled Variables in Propeller Assembly, page 103, under the DAT

section’s Writing Propeller Assembly Code (Syntax 2).

 An explanation of Cog RAM contents when running Spin and Propeller Assembly, in

COGNEW, p. 78.

 Corrections to the arithmetic in the examples under the LONG section’s

Reading/Writing Longs of Main Memory (Syntax 3), p. 130.

 Note 5, regarding WAITVID, added to the notes for the Propeller Assembly Instruction

Master Table, p. 256. This information was also added to the instruction section,

p. 371.

1: Introducing the Propeller Chip

Chapter 1: Introducing the Propeller Chip

This chapter describes the Propeller chip hardware. To fully understand and use the Propeller

effectively, it’s important to first understand its hardware architecture. This chapter presents

the details of the hardware such as package types, package sizes, pin descriptions, and

functions.

Concept

The Propeller chip is designed to provide high-speed processing for embedded systems while

maintaining low current consumption and a small physical footprint. In addition to being

fast, the Propeller provides flexibility and power through its eight processors, called cogs,

that can perform simultaneous independent or cooperative tasks, all while maintaining a

relatively simple architecture that is easy to learn and utilize.

The resulting design of the Propeller frees application developers from common complexities

of embedded systems programming. For example:

 The memory map is flat. There is no need for paging schemes with blocks of code,

data or variables. This is a big time-saver during application development.

 Asynchronous events are easier to handle than they are with devices that use

interrupts. The Propeller has no need for interrupts; just assign some cogs to

individual, high-bandwidth tasks and keep other cogs free and unencumbered. The

result is a more responsive application that is easier to maintain.

 The Propeller Assembly language features conditional execution and optional result

writing for each individual instruction. This makes critical, multi-decision blocks of

code more consistently timed; event handlers are less prone to jitter and developers

spend less time padding, or squeezing, cycles here and there.

Propeller Manual v1.2 · Page 13

Introducing the Propeller Chip

Package Types

The Propeller chip is available in the package types shown here.

P8X32A-Q44

4

-

p

in LQFP

P8X32A-D40 40-pin DIP

P8X32A-M44

4

-

p

in QFN

Page 14 · Propeller Manual v1.2

1: Introducing the Propeller Chip

Pin Descriptions

Table 1-1: Pin Descriptions

Pin Name Direction Description

P0 – P31 I/O

General purpose I/O Port A. Can source/sink 40 mA each at 3.3 VDC.

Logic threshold is  ½ VDD; 1.65 VDC @ 3.3 VDC.

The pins shown below have a special purpose upon power-up/reset but are

general purpose I/O afterwards.

P28 - I2C SCL connection to optional, external EEPROM.

P29 - I2C SDA connection to optional, external EEPROM.

P30 - Serial Tx to host.

P31 - Serial Rx from host.

VDD --- 3.3 volt power (2.7 – 3.3 VDC).

VSS --- Ground.

BOEn I

Brown Out Enable (active low). Must be connected to either VDD or VSS.

If low, RESn becomes a weak output (delivering VDD through 5 K) for

monitoring purposes but can still be driven low to cause reset. If high,

RESn is CMOS input with Schmitt Trigger.

RESn I/O

Reset (active low). When low, resets the Propeller chip: all cogs disabled

and I/O pins floating. Propeller restarts 50 ms after RESn transitions from

low to high.

XI I

Crystal Input. Can be connected to output of crystal/oscillator pack (with

XO left disconnected), or to one leg of crystal (with XO connected to other

leg of crystal or resonator) depending on CLK Register settings. No

external resistors or capacitors are required.

XO O

Crystal Output. Provides feedback for an external crystal, or may be left

disconnected depending on CLK Register settings. No external resistors

or capacitors are required.

The Propeller (P8X32A) has 32 I/O pins (Port A, pins P0 through P31). Four of these I/O

pins, P28-P31 have a special purpose upon power-up/reset. At power-up/reset, pins P30 and

P31 communicate with a host for programming and P28 and P29 interface to an external

32 KB EEPROM (24LC256).

Propeller Manual v1.2 · Page 15

Introducing the Propeller Chip

Page 16 · Propeller Manual v1.2

Specifications

Table 1-2: Specifications

Model P8X32A

Power Requirements 3.3 volts DC. (Max current draw must be limited to 300 mA).

External Clock Speed DC to 80 MHz (4 MHz to 8 MHz with Clock PLL running)

System Clock Speed DC to 80 MHz

Internal RC Oscillator 12 MHz or 20 kHz (approximate; may range from 8 MHz – 20 MHz,

or 13 kHz – 33 kHz, respectively)

Main RAM/ROM 64 K bytes; 32 KB RAM + 32 KB ROM

Cog RAM 512 x 32 bits each

RAM/ROM Organization Main RAM: Long (32-bit), Word (16-bit), or Byte (8-bit) addressable

Cog RAM: Long (32-bit) addressable only

I/O pins 32 CMOS signals with VDD/2 input threshold.

Current Source/Sink per I/O 40 mA

Current Draw @ 3.3 vdc, 70 °F 500 µA per MIPS (MIPS = Freq in MHz / 4 * Number of Active Cogs)

1: Introducing the Propeller Chip

Hardware Connections

Figure 1-1 shows an example wiring diagram that provides host and EEPROM access to the

Propeller chip. In this example the host access is achieved through the Propeller Plug device

(a USB to TTL serial converter).

Figure 1-1: Example wiring diagram that allows for programming the Propeller chip

nd an external 32 Kbyte EEPROM, and running the Propeller with an external crystal. a

Propeller Manual v1.2 · Page 17

Introducing the Propeller Chip

Boot Up Procedure

Upon power-up (+ 100 ms), RESn low-to-high, or software reset:

1. The Propeller chip starts its internal clock in slow mode (≈ 20 kHz), delays for 50 ms

(reset delay), switches the internal clock to fast mode (≈ 12 MHz), and then loads and

runs the built-in Boot Loader program in the first processor (Cog 0).

2. The Boot Loader performs one or more of the following tasks, in order:

a. Detects communication from a host, such as a PC, on pins P30 and P31. If

communication from a host is detected, the Boot Loader converses with the

host to identify the Propeller chip and possibly download a program into

Main RAM and optionally into an external 32 KB EEPROM.

b. If no host communication was detected, the Boot Loader looks for an

external 32 KB EEPROM (24LC256) on pins P28 and P29. If an EEPROM

is detected, the entire 32 KB data image is loaded into the Propeller chip’s

Main RAM.

c. If no EEPROM was detected, the boot loader stops, Cog 0 is terminated, the

Propeller chip goes into shutdown mode, and all I/O pins are set to inputs.

3. If either step 2a or 2b was successful in loading a program into the Main RAM, and a

suspend command was not given by the host, then Cog 0 is reloaded with the built-in

Spin Interpreter and the user code is run from Main RAM.

Run-Time Procedure

A Propeller Application is a user program compiled into its binary form and downloaded to

the Propeller chip’s RAM and, possibly, external EEPROM. The application consists of code

written in the Propeller chip’s Spin language (high-level code) with optional Propeller

Assembly language components (low-level code). Code written in the Spin language is

interpreted during run time by a cog running the Spin Interpreter while code written in

Propeller Assembly is run in its pure form directly by a cog. Every Propeller Application

consists of at least a little Spin code and may actually be written entirely in Spin or with

various amounts of Spin and assembly. The Propeller chip’s Spin Interpreter is started in

Step 3 of the Boot Up Procedure, above, to get the application running.

Once the boot-up procedure is complete and an application is running in Cog 0, all further

activity is defined by the application itself. The application has complete control over things

like the internal clock speed, I/O pin usage, configuration registers, and when, what and how

Page 18 · Propeller Manual v1.2

1: Introducing the Propeller Chip

Propeller Manual v1.2 · Page 19

many cogs are running at any given time. All of this is variable at run time, as controlled by

the application, including the internal clock speed.

Shutdown Procedure

When the Propeller goes into shutdown mode, the internal clock is stopped causing all cogs

to halt and all I/O pins are set to input direction (high impedance). Shutdown mode is

triggered by one of the three following events:

1) VDD falling below the brown-out threshold (≈2.7 VDC), when the brown-out circuit

is enabled,

2) the RESn pin going low, or

3) the application requesting a reboot (see the REBOOT command, page 187).

Shutdown mode is discontinued when the voltage level rises above the brown-out threshold

and the RESn pin is high.

Introducing the Propeller Chip

Block Diagram

Figure 1-2: Propeller Chip Block Diagram

Page 20 · Propeller Manual v1.2

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