NXP Semiconductors MPC5644A, Reference Manual, Page: 1161 / 1735

Enhanced Queued Analog-to-Digital Converter (EQADC)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor 1161
2. Configure the Section 25.5.2.7, EQADC CFIFO Control Registers (EQADC_CFCR) .
a) Write “1” to CFINV5 in EQADC_FCR2. This will invalidate the contents of CFIFO5.
b) Set MODE5 to Continuous-Scan Software Trigger mode in EQADC_CFCR2.
3. To transfer a command, write it to EQADC CFIFO Push Register 5 (EQADC_CFPR5) with
Message Tag = 0b0101. Refer to Section 25.5.2.5, EQADC CFIFO Push Registers
(EQADC_CFPR) .
4. Up to four commands can be queued in CFIFO5. Check the CFCTR5 status in EQADC_FISR5
before pushing another command to avoid overflowing the CFIFO. Refer to Section 25.5.2.9,
EQADC FIFO and Interrupt Status Registers (EQADC_FISR) .
5. When the EQADC receives a conversion result for RFIFO5, it generates an interrupt request.
RFIFO Pop Register 5 (EQADC_RFPR5) can be popped to read the result. Refer to
Section 25.5.2.6, EQADC Result FIFO Pop Registers (EQADC_RFPR) .
25.7.4 Modifying queues
More CQueues may be needed than the six supported by the EQADC. These additional CQueues can be
supported by interrupting command transfers from a configured CFIFO, even if it is TRIGGERED and
transferring, modifying the corresponding CQueue in the RAM or associating another CQueue to it, and
restarting the CFIFO. More details on disabling a CFIFO are described in
Section 25.6.4.6.1, Disabled
Mode .
1. Determine the resumption conditions when later resuming the scan of the CQueue at the point
before it was modified.
a) Change MODEx in Section 25.5.2.7, EQADC CFIFO Control Registers (EQADC_CFCR) , to
Disabled. Refer to Section 25.6.4.6.1, Disabled Mode , for a description of what happens when
MODEx is changed to Disabled.
b) Poll CFSx until it becomes IDLE in Section 25.5.2.12, EQADC CFIFO Status Register
(EQADC_CFSR) .
c) Read and save TC_CFx in Section 25.5.2.10, EQADC CFIFO Transfer Counter Registers
(EQADC_CFTCR) , for later resuming the scan of the queue. The TC_CFx provides the point
of resumption.
d) Since all result data may not have being stored in the appropriate RFIFO at the time MODEx
is changed to disable, wait for all expected results to be stored in the RFIFO/RQueue before
reconfiguring the DMAC to work with the modified RQueue. The number of results that must
return can be estimated from the TC_CFx value obtained above.
2. Disable the DMAC from responding to the DMA request generated by CFFFx and RFDFx in
Section 25.5.2.9, EQADC FIFO and Interrupt Status Registers (EQADC_FISR) .
3. Write “0x0000” to the TC_CFx field.
4. Load the new configuration and conversion commands into RAM. Configure the DMAC to
support the new CQueue/RQueue, but do not configure it yet to respond to DMA requests from
CFIFOx/RFIFOx.
5. If necessary, modify Section 25.5.2.8, EQADC Interrupt and DMA Control Registers
(EQADC_IDCR) , to suit the modified CQueue.