Digital Control Subsystem

00

63

Conversion Command Word (CCW) Table

Beginning of Queue 1

End of Queue 1

Beginning of Queue 2

End of Queue 2

Channel Select,

Sample, Hold,

A/D Conversion

Result Word Table

00

63

10-bit Conversion Command

Word Format

9

8

[7:6]

[5:0]

P

BYP

IST

CHAN

P — Pause after Conversion until Next Trigger

BYP — Bypass Buffer Amplifier IST — Input Sample Time CHAN — Channel Number and

End-of-Queue Code

10-bit Result, Readable in

 

 

 

Three 16-BIT Formats

 

 

 

15 14 13 12 11 10

 

 

[9:0]

 

 

 

0

0

0

 

0

0

0

 

 

RESULT

 

 

 

Right-Justified, Unsigned Result

 

 

 

 

 

[15:6]

 

 

 

 

 

[5:0]

 

 

S

 

 

RESULT

 

0

 

0

0

 

0

0

0

 

 

Left-Justified, Signed Result

 

 

 

 

 

 

[15:6]

 

 

 

 

 

[5:0]

 

 

 

 

RESULT

 

 

0

 

0

0

 

0

0

0

Left-Justified, Unsigned Result

Figure 27-43. 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.

27-60

MCF5282 User’s Manual

MOTOROLA

Page 644
Image 644
Motorola MCF5282, MCF5281 user manual Qadc Conversion Queue Operation