© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
User manual Rev. 02 — 2 March 2005 19 of 105
Philips Semiconductors
UM10108
P89LPC924/925 User manual
3.2 A/D operating modes
3.2.1 Fixed channel, single conversion mode
A single input channel can be selected for conversion. A single conversion will be
performed and the result placed in the result register which corresponds to the selected
input channel (See
Ta bl e 6). An interrupt, if enabled, will be generated after the conversion
completes. The input channel is selected in the ADINS register. This mode is selected by
setting the SCAN1 bit in the ADMODA register.
3.2.2 Fixed channel, continuous conversion mode
A single input channel can be selected for continuous conversion. The results of the
conversions will be sequentially placed in the four result registers
Tab le 7. An interrupt, if
enabled, will be generated after every four conversions. Additional conversion results will
again cycle through the four result registers, overwriting the previous results. Continuous
conversions continue until terminated by the user. This mode is selected by setting the
SCC1 bit in the ADMODA register.
3.2.3 Auto scan, single conversion mode
Any combination of the four input channels can be selected for conversion by setting a
channel’s respective bit in the ADINS register. The channels are converted from LSB to
MSB order (in ADINS). A single conversion of each selected input will be performed and
the result placed in the result register which corresponds to the selected input channel
(See
Tab le 6). An interrupt, if enabled, will be generated after all selected channels have
been converted. If only a single channel is selected this is equivalent to single channel,
single conversion mode. This mode is selected by setting the SCAN1 bit in the ADMODA
register.
3.2.4 Auto scan, continuous conversion mode
Any combination of the four input channels can be selected for conversion by setting a
channel’s respective bit in the ADINS register. The channels are converted from LSB to
MSB order (in ADINS). A conversion of each selected input will be performed and the
result placed in the result register which corresponds to the selected input channel (See
Tab le 6). An interrupt, if enabled, will be generated after all selected channels have been
converted. The process will repeat starting with the first selected channel. Additional
Table 6: Input channels and Result registers for fixed channel single, auto scan single,
and autoscan continuous conversion modes.
Result register Input channel Result register Input channel
AD1DAT0 AD10 AD1DAT2 AD12
AD1DAT1 AD11 AD1DAT3 AD13
Table 7: Result registers and conversion results for fixed channel, continuous conversion
mode.
Result register Contains
AD1DAT0 Selected channel, first conversion result
AD1DAT1 Selected channel, second conversion result
AD1DAT2 Selected channel, third conversion result
AD1DAT3 Selected channel, forth conversion result