Enhanced Queued Analog-to-Digital Converter (eQADC)
MPC5566 Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 19-115
c) Read and save EQADC_CFTCRn[TC_CFn] (see Section 19.3.2.9, “eQADC CFIFO Transfer
Counter Registers 0–5 (EQADC_CFTCRn)”) for later resuming the scan of the queue. The
TC_CFn provides the point of resumption.
d) Since all result data may not have being stored in the appropriate RFIFO at the time MODEn
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_CFn value obtained above.
2. Disable the eDMA from responding to the eDMA request generated by EQADC_FISRn[CFFFn]
and EQADC_FISRn[RFDFn] (see Section 19.3.2.8, “eQADC FIFO and Interrupt Status Registers
0–5 (EQADC_FISRn)”).
3. Write “0x0000” to the TC_CFn 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
CFIFOn/RFIFOn.
5. If necessary, modify the EQADC_IDCRn registers (see Section 19.3.2.7, “eQADC Interrupt and
eDMA Control Registers 0–5 (EQADC_IDCRn)”) to suit the modified command queue.
6. Write 1 to EQADC_CFCRn[CFINVn] (see Section 19.3.2.6, “eQADC CFIFO Control Registers
0–5 (EQADC_CFCRn)”) to invalidate the entries of CFIFOn.
7. Configure the eDMA to respond to eDMA requests generated by CFFFn and RFDFn.
8. Change MODEn to the modified CFIFO operation mode. Write 1 to SSEn to trigger CFIFOn if
MODEn is software trigger.
19.5.5 Command Queue and Result Queue Usage
Figure 19-67 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 19-67, 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.
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