MCF5282UM Datasheet, PDF (592/766 Pages) Freescale Semiconductor, Inc – MCF5282 and MCF5216 ColdFire Microcontroller User s Manual

Queued Analog-to-Digital Converter (QADC)
Conversion Command
Word (CCW) Table
00
Beginning of Queue 1
Result Word Table
00
•
•
•
•
•
•
End of Queue 1
Channel Select,
Beginning of Queue 2
Sample, Hold,
A/D Conversion
•
•
•
63
End of Queue 2
•
•
•
63
10-bit Conversion Command
Word Format
10-bit Result, Readable in
Three 16-BIT Formats
9 8 [7:6]
[5:0]
15 14 13 12 11 10
[9:0]
P BYP IST
CHAN
000000
RESULT
Right-Justified, Unsigned Result
P — Pause after Conversion
until Next Trigger
BYP — Bypass Buffer Amplifier
IST — Input Sample Time
CHAN — Channel Number and
End-of-Queue Code
[15:6]
[5:0]
S
RESULT
000000
Left-Justified, Signed Result
[15:6]
[5:0]
RESULT
000000
Left-Justified, Unsigned Result
Figure 28-43. QADC Conversion Queue Operation
To prepare the QADC for a scan sequence, write to the CCW table to specify the desired channel
conversions. The criteria for queue execution is established by selecting the queue operating mode. The
queue operating mode determines what type of trigger event starts queue execution. A trigger event refers
to any of the ways that cause the QADC to begin executing the CCWs in a queue or subqueue. An external
trigger is only one of the possible trigger events.
A scan sequence may be initiated by:
• A software command
• Expiration of the periodic/interval timer
• An external trigger signal
• An external gated signal (queue 1 only)
The queue can be scanned in single pass or continuous fashion. When a single-scan mode is selected, the
scan must be engaged by setting the single-scan enable bit. When a continuous-scan mode is selected, the
queue remains active in the selected queue operating mode after the QADC completes each queue scan
sequence.
During queue execution, the QADC reads each CCW from the active queue and executes conversions in
three stages:
• Initial sample
• Final sample
28-54
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3
Freescale Semiconductor