MPC563XM Reference Manual, Rev. 1
1040
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
Figure 24-62. CFIFO0 in Streaming Mode Entry Pointer Example (Cont.)
24.6.4.2.4
Streaming Mode Error Conditions
In the repeat state, the existing error conditions still apply, but now there are new ways to trigger them.
Now, the CCWs are not being invalidated so the DMA is not able to load more CCWs into those locations.
So a queue overflow becomes more likely, and occurs if the repeat loop is longer than 8 entries. If all
CCWs in the CFIFO0 are executed and no Pause bit or EOQ bit is detected, the eQADC will signal an
underflow error. In practice this may limit a repeating queue to 7 entries since otherwise an underflow will
occur at the point a Repeat with Advance trigger occurs, and there is no command in the CFIFO0 to
execute. The exception is a final command with both a Pause and an EOQ bit set. The End of Queue bit
EOQ continues to operate as in normal mode, unless the Repeat mode is enabled. In this case the Pause bit
takes presidence and a Repeat trigger causes the jump back described. A Repeat trigger with Advance
trigger causes the queue to end.
Another error condition occur when the repeat trigger is in the TRIGGERED state and a new repeat trigger
is received. In this case, a trigger overflow occurs but the CFIFO0 is defined to not restart the loop. The
trigger in this case is not used in the CFIFO0, but the overflow is indicated.
24.6.4.3
CFIFO Common Prioritization and Command Transfer
The CFIFO priority is fixed according to the CFIFO number. A CFIFO with a smaller number has a higher
priority. When commands of distinct CFIFOs are bound for the same destination (CBuffer), the higher
No entries pushed.
Last In
Push
Transfer
CFIFO0
Entries pushed. Fifo full. Waiting
Next
Data
Pointer
Next
Data
Pointer
Repeat
Pointer
Repeat
Pause
Transfer
CFIFO0
Next
Data
Pointer
Last In
Push
Next
Data
Pointer
Pause
Repeat
Pointer
Repeat
Entries executed to
pause bit.
Pending trigger.
at pause bit for Repeat trigger or
Advance & Repeat trigger.