pc87591l National Semiconductor Corporation, pc87591l Datasheet - Page 97

• Manufacturer Part Number: pc87591l
• Description: Lpc Mobile Embedded Controllers
• Manufacturer: National Semiconductor Corporation

Embedded Controller Modules
(Continued)
4.2.9
Usage Hints
Do not write to ADCAn, ADCBn or BLTCn and do not change the value of TCS, IND, DIR, OT, ADA, INCA, ADB and
INCB fields of DMACNTLn register while the associated channel is active (CHAC bit in DMASTATn register is 1).
When initializing these registers, write to BLTCn register last, since writing to BLTCn register activates the channel
immediately (if CHEN bit in DMACNTLn register is set to 1).
The ADRAn, ADRBn and BLTRn registers store transfer parameters (source address, destination address and block
length) for the next data block to be transferred, for either Auto-Initialize or Double-Buffer modes of operation. When
initializing these registers, write the BLTRn register last, since this validates the next block’s parameters (VLD bit in
DMASTATn register is set to 1).
The TCS bit in DMACNTLn register is programed according to the bus width of the devices. It determines how many
bytes are transferred in each DMA bus cycle.
The DMAC does not support non-aligned transfers. The values written to ADCAn, ADRAn, ADCBn and ADRBn must
be multiples of the Transfer Cycle Size (as defined by TCS bit in DMACNTLn register).
Revision 1.07
97
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