Freescale Semiconductor MPC5565, Reference Manual

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Enhanced Queued Analog-to-Digital Converter (eQADC)
MPC5565 Microcontroller Reference Manual, Rev. 1.0
18-116 Freescale Semiconductor
c) Read and save EQADC_CFTCRn[TC_CF n ] (see Section 18.3.2.9, “eQADC CFIFO Transfer
Counter Registers 0–5 (EQADC_CFTCRn) ”) for later resuming the scan of the queue. The
TC_CF n provides the point of resumption.
d) Since all result data may not have being stored in the appropriate RFIFO at the time MODE n
is changed to disable, wait for all expected results to be stored in the RFIFO/result queue before
reconfiguring the eDMA to work with the modified result queue. The number of results that
must return can be estimated from the TC_CF
n value obtained above.
2. Disable the eDMA from responding to the eDMA request generated by EQADC_FISRn[CFFF n ]
and EQADC_FISRn[RFDF n ] (see Section 18.3.2.8, “eQADC FIFO and Interrupt Status Registers
0–5 (EQADC_FISRn) ”).
3. Write “0x0000” to the TC_CF n field.
4. Load the new configuration and conversion commands into RAM. Configure the eDMA to support
the new command/result queue, but do not configure it yet to respond to eDMA requests from
CFIFO
n /RFIFO n .
5. If necessary, modify the EQADC_IDCRn registers (see Section 18.3.2.7, “eQADC Interrupt and
eDMA Control Registers 0–5 (EQADC_IDCRn) ”) to suit the modified command queue.
6. Write 1 to EQADC_CFCRn[CFINV n ] (see Section 18.3.2.6, “eQADC CFIFO Control Registers
0–5 (EQADC_CFCRn) ”) to invalidate the entries of CFIFO n .
7. Configure the eDMA to respond to eDMA requests generated by CFFF n and RFDF n .
8. Change MODE n to the modified CFIFO operation mode. Write 1 to SSE n to trigger CFIFO n if
MODE n is software trigger.
18.5.5 Command Queue and Result Queue Usage
Figure 18-67 is an example of command queue and result queue usage. It shows the command queue 0
commands requesting results that are stored in result queue 0 and result queue 1, and command queue 1
commands requesting results that are stored only in result queue 1. Some command messages request data
to be returned from the on-chip ADC/external device, but some only configure them and do not request
returning data. When a command queue contains both write and read commands like command queue 0,
the command queue and result queue entries are not aligned, in
Figure 18-67 , the result for the second
command of command queue 0 is the first entry of result queue 0. The figure also shows that command
queue and result queue entries can also become unaligned even if all commands in a command queue
request data as command queue 1. Command queue 1 entries became unaligned to result queue 1 entries
because a result requested by the forth command queue 0 command was sent to result queue 1. This
happens because the system can be configured so that several command queues can have results sent to a
single result queue.