Enhanced Queued Analog-to-Digital Converter (EQADC)
Freescale Semiconductor
27-121
PXR40 Microcontroller Reference Manual, Rev. 1
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. Refer to the DMAC block guide
for details about how this functionality is supported.
•
The corresponding DMA channel should be disabled. This might be desirable for CFIFOs in single
scan mode.
•
The source address should be updated to point 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 27-74. CQueue/CFIFO Interface
27.8.2.2
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. Refer to the DMAC
block guide for details about how this functionality is supported.
•
The corresponding DMA channel should be disabled.
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 PXR4030
Page 1: ...PXR40 Microcontroller Reference Manual Devices Supported PXR4030 PXR4040 PXR40RM Rev 1 06 2011...
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