MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor 19-75
Figure 19-40. Trigger Overrun on Level-Trigger Mode CFIFOs
NOTE
The trigger overrun flag will not set for CFIFOs configured for software
trigger mode.
19.4.3.6.5 Command Sequence Non-Coherency Detection
The eQADC provides a mechanism to indicate if a command sequence has been completely executed
without interruptions. A command sequence is defined as a group of consecutive commands bound for the
same ADC and it is expected to be executed without interruptions. A command sequence is coherent if its
commands are executed in order without interruptions. Because commands are stored in the ADC’s
command buffers before being executed in the eQADC, a command sequence is coherent if, while it is
transferring commands to an on-chip ADC command buffer, the buffer is only fed with commands from
that sequence without ever becoming empty.
A command sequence starts when:
• A CFIFO in TRIGGERED state transfers its first command to an on-chip ADC.
• The CFIFO is constantly transferring commands and the previous command sequence ended.
• The CFIFO resumes command transfers after being interrupted.
And a command sequence ended when:
• An asserted EOQ bit is detected on the last transferred command.
• CFIFO is in edge-trigger mode and asserted pause bit is detected on the last transferred command.
• The ADC to which the next command is bound is different from the ADC to which the last
command was transferred.
Figure 19-41 shows examples of how the eQADC would detect command sequences when transferring
commands from a CFIFO. The smallest possible command sequence can have a single command as shown
in example 3 of Figure 19-41.
Command Transmission
through eQADC SSI
CFIFO Status
TORF
Command 1 Null Message Command 2
Triggered WFT Triggered Triggered
WFT
Low Active
Level Trigger
If gate closes during a command transmission, it is only
recognized when the transmission ends.
1) CFIFO programmed to ‘continuous-scan low level gated external trigger mode’.
2) Command 2 has its ABORT_ST bit negated.
Assumptions:
3) There are no other CFIFOs using the serial interface.
WFT = Waiting for Trigger
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