Motorola MPC533 Reference Manual page 474

Programming the QADC64E Registers
Bits Name
0:5 — Reserved
6 P Pause. The pause bit allows the creation of sub-queues within queue 1 and queue 2. The
QADC64E performs the conversion specified by the CCW with the pause bit set, and then the
queue enters the pause state. Another trigger event causes execution to continue from the pause
to the next CCW.
0 = Do not enter the pause state after execution of the current CCW.
1 = Enter the pause state after execution of the current CCW.
7 BYP Sample amplifier bypass. Setting BYP enables the amplifier bypass mode for a conversion, and
subsequently changes the timing. Refer to 13.4.1.2 Amplifier Bypass Mode Conversion Timing
for more information.
0 = Amplifier bypass mode disabled.
1 = Amplifier bypass mode enabled.
8:9 IST Input sample time. The IST field specifies the length of the sample window. Longer sample times
permit more accurate A/D conversions of signals with higher source impedances, especially if
BYP = 1.
00 = QCKL period x 2
01 = QCKL period x 4
10 = QCKL period x 8
11 = QCKL period x 16
10:15 CHAN Channel number. The CHAN field selects the input channel number corresponding to the analog
input signal to be sampled and converted. The analog input signal channel number assignments
and the signal definitions vary depending on whether the QADC64E is operating in multiplexed
or non-multiplexed mode. The queue scan mechanism sees no distinction between an internally
or externally multiplexed analog input.
If CHAN specifies a reserved channel number (channels 32 to 47) or an invalid channel number
(channels 4 to 31 in non-multiplexed mode), the low reference level (VRL) is converted.
Programming the channel field to channel 63 indicates the end of the queue. Channels 60 to 62
are special internal channels. When one of these channels is selected, the sample amplifier is not
used. The value of VRL, VRH, or (V
the input sample time to any value other than two for one of the internal channels has no benefit
except to lengthen the overall conversion time.
Table 13-20 shows the channel number assignments for non-multiplexed mode. Table 13-21
shows the channel number assignments for multiplexed mode.
The channel field is programmed for channel 63 to indicate the end of the queue. Channels
60 to 62 are special internal channels. When one of the special channels is selected, the
sampling amplifier is not used. The value of V
onto the converter. Also for the internal special channels, programming any input sample
time other than two has no benefit except to lengthen the overall conversion time.
13.3.10 Result Word Table
The result word table is a RAM, 64 words long and 10 bits wide. An entry is written by the
QADC64E after completing an analog conversion specified by the corresponding CCW
table entry. Software can read or write the result word table, but in normal operation, the
software reads the result word table to obtain analog conversions from the QADC64E.
13-30
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Table 13-13. CCW Bit Descriptions
– V
RH
RL
MPC533 Reference Manual
Description
)/2 is placed directly into the converter. Programming
RL
, V , or (V - V
RH RH RL
)/2 is placed directly
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