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Enhanced Queued Analog-to-Digital Converter (EQADC)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
1159
25.7.2
EQADC/DMAC Interface
This section provides an overview about the EQADC/DMAC interface and general guidelines about how
the DMAC should be configured in order for it to correctly transfer data between the queues in system
memory and the EQADC FIFOs.
NOTE
Advanced DMACs provide more functionality then the ones discussed in
this section.
25.7.2.1
CQueue/CFIFO transfers
In transfers involving CQueues and CFIFOs, the DMAC moves data from a queued source to a single
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. The DMAC contains a data
structure containing these addresses and other parameters used in the control of data transfers. For every
DMA request issued by the EQADC, the DMAC has to be configured to transfer a single command (32-bit
data) from the CQueue, pointed to by the source address, to the CFIFO push register, pointed to by the
destination address. After the service of a DMA request is completed, the source address has to be updated
to point to the next valid command. The destination address remains unchanged. When the last command
of a queue is transferred one of the following actions is recommended.
•
The corresponding DMA channel should be disabled. This might be desirable for CFIFOs in single
scan mode.
•
The source address should be updated to pointed to a valid command which can be the first
command in the queue that has just been transferred (cyclic queue), or the first command of any
other CQueue. This is desirable for CFIFOs in continuous scan mode, and at some cases, for
CFIFOs in single scan mode.
Figure 25-96. CQueue/CFIFO Interface
Source Address
Command 1
Command 2
Command 3
.....
Command n-1
Command n
CFPRx
CQueue in
system memory
CFIFO
Push Register
One command transfer per DMA
request
Destination Address
Summary of Contents for MPC5644A
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Page 1228: ...Decimation Filter MPC5644A Microcontroller Reference Manual Rev 6 1228 Freescale Semiconductor...
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