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Enhanced Queued Analog-to-Digital Converter (EQADC)
MPC5644A Microcontroller Reference Manual, Rev. 6
1160
Freescale Semiconductor
25.7.2.2
RQueue/RFIFO transfers
In transfers involving RQueues and RFIFOs, the DMAC moves data from a single source to a queue
destination as showed in
. The location of the data to be moved is indicated by the source
address, and the final destination for that data, by the destination address. For every DMA request issued
by the EQADC, the DMAC has to be configured to transfer a single result (16-bit data), pointed to by the
source address, from the RFIFO pop register to the RQueue, pointed to by the destination address. After
the service of a DMA request is completed, the destination address has to be updated to point to the
location where the next 16-bit result will be stored. The source address remains unchanged. When the last
expected result is written to the RQueue, one of the following actions is recommended.
•
The corresponding DMA 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 RQueue (cyclic queue), or the beginning of a
new RQueue.
Figure 25-97. RQueue/RFIFO Interface
25.7.3
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. The results will be returned to RFIFO5.
1. Configure the
Section 25.5.2.8, EQADC Interrupt and DMA Control Registers (EQADC_IDCR)
a) Clear CFIFO Fill Enable5 (CFFE5 = 0) in EQADC_IDCR2.
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_IDCR2.
Result 1
Result 2
Result 3
.....
Result n-1
Result n
RFPRx
RQueue in
system memory
RFIFO
Pop Register
One result transfer per DMA
request
Source Address
Destination Address
Summary of Contents for MPC5644A
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