Motorola MPC533 Reference Manual page 449

13.2.4 Using the Queue and Result Word Table
The heart of the QADC is its conversion command word (CCW) queues. This is where the
module is programmed to convert a particular channel according to a particular
requirement. The queues are created by writing CCWs into the CCW table in the register
memory. The queues are controlled by the three control registers, and their status can be
read from the two status registers. As conversions are completed the digital value is written
into the result word table. Figure 13-2 shows the CCW queue and the result word table.
Conversion Command
Word (CCW) Table
00
Begin Queue 1
End of Queue 1
BQ2
Begin Queue 2
End of Queue 2
MSB
6 7
P BYP IST
P = Pause Until Next Trigger
BYP = Bypass Buffer Amplifier
IST = Input Sample Time
CHAN = Channel Number and End_of_Queue Code
10-bit Conversion
Command Word
(CCW) Format
Figure 13-2. QADC64E Conversion Queue Operation
13.2.5 External Multiplexing
The QADC can use from one to four 8-input external multiplexer chips to expand the
number of analog signals that may be converted. The externally multiplexed channels are
automatically selected from the channel field of the conversion command word (CCW)
table. External Multiplex mode is software selectable, by setting the EMUX bit of control
register 0, QACR0.
MOTOROLA Chapter 13. Queued Analog-to-Digital Converter Legacy Mode Operation
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Key Features, Overview, and Quick Reference Diagrams
Channel Select,
Sample, Hold,
Analog to Digital
LSB
8 9 10 15
CHAN
Result Word Table
A/D Converter
and
Conversion
MSB
5 6
0
0 0 0 0 0 0
Right Justified, Unsigned Result Format
0 1
S Result
Left Justified, Signed Result Format
0
Result
Left Justified, Unsigned Result Format
10-bit Result is
Software Readable
in Three Different 16-bit Formats
00
LSB
15
Result
15
9 10
0 0 0 0 0 0
15
9 10
0 0 0 0 0 0
13-5