MPC555
/
MPC556
QUEUED ANALOG-TO-DIGITAL CONVERTER MODULE-64
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
13-47
Table 13-19 CCW Bit Descriptions
Bit(s)
Name
Description
0:5
—
Reserved
6
P
Pause. The pause bit allows the creation of sub-queues within queue 1 and queue 2. The
QADC64 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
13.9.1.1 Amplifier Bypass Mode Conversion Tim-
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 pin to be sampled and converted. The analog input pin channel number assignments and
the pin definitions vary depending on whether the QADC64 is operating in multiplexed or non-
multiplexed mode. The queue scan mechanism sees no distinction between an internally or ex-
ternally 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. Program-
ming the channel field to channel 63 indicates the end of the queue. Channels 60 to 62 are spe-
cial internal channels. When one of these channels is selected, the sample amplifier is not used.
The value of VRL, VRH, or (V
RH
– V
RL
)/2 is placed directly into the converter. Programming the
input sample time to any value other than two for one of the internal channels has no benefit ex-
cept to lengthen the overall conversion time.
shows the channel number assignments for the non-multiplexed mode.
shows the channel number assignments for the multiplexed mode.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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