MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
19-110
Freescale Semiconductor
•
The corresponding eDMA channel should be disabled.
•
The destination address should be updated pointed to the next location where new coming results
are stored, which can be the first entry of the current receive queue (cyclic queue), or the beginning
of a new receive queue.
Figure 19-66. Receive Queue/RFIFO Interface
19.5.3
Sending Immediate Command Setup Example
In the eQADC, there is no immediate command register for sending a command immediately after writing
to that register. However, a CFIFO can be configured to perform the same function as an immediate
command register. The following steps illustrate how to configure CFIFO5 as an immediate command
CFIFO. This eliminates the use of the eDMA. The results will be returned to RFIFO5.
1. Configure the
Section 19.3.2.7, “eQADC Interrupt and eDMA Control Registers 0–5
a) Clear CFIFO fill enable5 (CFFE5 = 0) in EQADC_IDCR5.
b) Clear CFIFO underflow interrupt enable5 (CFUIE5 = 0) in EQADC_IDCR2.
c) Clear RFDS5 to configure the eQADC to generate interrupt requests to pop result data from
RFIF05.
d) Set RFIFO drain enable5 (RFDE5 = 1) in EQADC_IDCR5.
2. Configure the
Section 19.3.2.6, “eQADC CFIFO Control Registers 0–5 (EQADC_CFCRn)
.”
a) Write 1 to CFINV5 in EQADC_CFCR5. This will invalidate the contents of CFIFO5.
b) Set MODE5 to continuous-scan software trigger mode in EQADC_CFCR5.
3. To transfer a command, write it to the eQADC CFIFO push register 5 (EQADC_CFPR5) with
message tag = 0b0101. Refer to
Section 19.3.2.4, “eQADC CFIFO Push Registers 0–5
4. Up to 4 commands can be queued in CFIFO5. Check the CFCTR5 status in EQADC_FISR5
before pushing another command to avoid overflowing the CFIFO. Refer to
“eQADC FIFO and Interrupt Status Registers 0–5 (EQADC_FISRn)
.”
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 19.3.2.5, “eQADC Result FIFO Pop Registers 0–5 (EQADC_RFPRn)
Result 1
Result 2
Result 3
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Result n-1
Result n
One result transfer
per DMA request
RFPRx
Source Address
Destination Address
RFIFO Pop Register
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Summary of Contents for MPC5553
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