CHAPTER 12 DMA FUNCTIONS
318
(2) DMA on-chip RAM address registers 0 to 2 (DRA0 to DRA2)
These registers are used to set the on-chip RAM address for DMA channel n. An incrementation function is
provided.
The incrementation value is “1” during 8-bit transfers and “2” during 16-bit transfers.
The following DMA transfer addresses are retained during DMA transfers.
Read and write in 16-bit units are enabled.
Caution
Do not set an odd-numbered address for a 16-bit transfer (DS = 1 in the DCHCn register).
Figure 12-2. Format of DMA On-chip RAM Address Registers 0 to 2 (DRA0 to DRA2)
After reset:
undefined
R/W
Address : DRA0
FFFFF182H
DRA1
FFFFF192H
DRA2
FFFFF1A2H
15
14
13
12
0
DRAn
0
0
0
RAn12-RAn0
(n = 0-2)
(3) DMA byte count registers 0 to 2 (DBC0 to DBC2)
These are 8-bit registers that are used to set the number of transfers for DMA channel n.
The remaining number of transfers is retained during the DMA transfers.
A value of 1 is decremented once per transfer if the transfer is a byte (8-bit) transfer or a value of 2 is
decremented once per transfer if the transfer is a 16-bit transfer. The transfers are ended when a borrow
operation occurs. Accordingly, “number of transfers
−
1” should be set for byte transfers and “(number of
transfers
−
1)
×
2” should be set for 16-bit transfers.
Read and write in 8-bit units are enabled.
During 16-bit transfers, values set to bit 0 are ignored and a “0” is set to bit 0 after each decrementation.
Figure 12-3. Format of DMA Byte Count Registers 0 to 2 (DBC0 to DBC2)
After reset:
undefined
R/W
Address : DBC0
FFFFF184H
DBC1
FFFFF194H
DBC2
FFFFF1A4H
7
0
DBCn
BCn7-BCn0
(n = 0-2)
Caution
Values set to bit 0 are ignored during 16-bit transfers.
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