S90-010 CS FRICK QUANTUM COMPRESSOR CONTROL PANEL
Page 12 COMMUNICATIONS SETUP
Quantum’s "$" Protocol Specifications
Quantum’s (“$”) protocol commands have been added
specifically for the Quantum. Unless otherwise shown, 9
characters are returned from the Quantum for a data
value. The data value includes two decimal fields and the
first character position is either; “-“ if the value is negative,
or it is “+” if the value is positive. For example, if the
data’s value is 25.5; then the value +00002550 is sent. All
temperatures are in degree C and all pressures are in
PSIA. A mode such as Slide Valve mode is returned as
an integer value that represents the mode it is in. For
example, a +00000000 is sent if it is in manual, or a
+00000100 is sent if it is in automatic, or a +00000200 is
sent if it is in remote. The value zero +00000000 is used
to represent an “OFF” status and a “DISABLED” option.
The value one +00000100, which is received as a 1, is
used to represent an “ON” status and an “ENABLED”
option. Setpoints are only changed if the value sent is
within the acceptable range. Reference the “Frick
Quantum Control Panel Maintenance” publication S90-010
M for the setpoints default settings and ranges. The
checksum is the 2 byte hexadecimal sum of each
character within the command or returned answer
excluding the command type identifier, ”$”. If the
command’s checksum is replaced with “??”, the Quantum
returns a response without using checksum error checking
on the received command (refer to the “Data Packet”
section for more information). If the Quantum detects a
checksum error, a “N” (Not Acknowledged), the
Compressor ID code, “02”, Carriage return, and Linefeed
are returned.
This document will demonstrate how to communicate to the
Quantum panel using the tables that appear on the
following pages.
Data Packet
If you were interested in viewing the information that is
displayed on the “Operating Status - Page 1” screen
(“Home” screen), you would want to refer to the table
entitled “RETURN OPERATING STATUS Page 1 data:
$01D1” table on the next page.
The quickest and easiest way to demonstrate this protocol
is through Hyperterminal (see the section entitled
“Hyperterminal” later in this manual). After setting up
Hyperterminal and ensuring that all wiring and jumper
configurations are correct, type a “$” symbol. This is the
character that will alert all the Quantums on the
communications line that data is on its way. Following the
“$” symbol, type the ID code of the Quantum that you wish
to query (for instance “01” for the first Quantum). After the
ID number, type a “D1”. The protocol code in the Quantum
recognizes this portion of the data packet as a request for
the data that is displayed on the “Operating Status - Page
1” screen.
Up to now you have typed the following information:
“$01D1”. The next thing that must be done is to enter a
checksum value. You may elect to type in a “??” as a
wildcard if you do not have the time to figure the correct
checksum, however, the information that is returned may or
may not always be reliable. The checksum will ensure
reliability.
To arrive at the checksum value for the command you have
just typed, you will need to convert each ASCII digit into
hexadecimal (do not include the “$” symbol). For this
example, you will need to take the first digit “0”, and
referring to the Conversion Chart at the end of this section,
look down the ASCII column until you find “0”. You will
notice that the Hexadecimal equivalent for ASCII “0” is “30”
hex. Repeat the process of looking up each digit in the
ASCII column, and finding its equivalent in the
Hexadecimal column, and write each value down. When all
four digits (01D1) have been converted to hexadecimal,
you will need to add the four values together. Remember,
the values are in hexadecimal format, not decimal. If you
are not familiar with hexadecimal math, you may wish to
utilize the calculator that comes with Microsoft Windows.
Look at the following chart:
ASCII Value of
Data Packaet Hexadecimal
Equivalent
030
131
D44
131
Hex Total = D6
The answer that is arrived at from the previous chart is
“D5”. This will become the checksum for the data packet,
and is appended to the end of the data that has so far been
typed in.
NOTE: For any calculation that results in an answer of
more than two digits, use only the right most two
digits, and disregard all digits to the left.
The result should look like this:
$01D1D6
Press the [Enter] key. You should see an immediate
response. The format of this response should resemble
something (but not necessarily exactly) like:
A01+00006166+00008618+00008272+00002974+000154
15+00005314+00008501+00000000+00000000+0000000
0+00000341+00000231-00027249B6
Referring to the “RETURN OPERATING STATUS Page 1
data: $01D1” table on the next page, we find that the first
line of the response, “A01”, indicates that an
Acknowledgement (A) was received from device 01 (01).
This is followed by “+00006166” (Suction Pressure). The
plus (+) symbol indicates a positive value, followed by
“00006166”. Since there are two decimal positions
assumed, “0006166” equals 61.66 psia. Using the “+/-”
symbols as a delimiter in the above example, each section
of 8 digits can be interpreted by comparing it with the
“Operating Status” table. The “B6” value at the very end of
the response is the checksum value that the Quantum
returned, not actual data.