258
8.5.7
Block Transfer Mode
In block transfer mode, transfer is performed with channels A and B used in combination. Block
transfer mode can be specified by setting the FAE bit in DMABCR and the BLKE bit in
DMACRA to 1.
In block transfer mode, a transfer of the specified block size is carried out in response to a single
transfer request, and this is executed the specified number of times. The transfer source is
specified by MARA, and the transfer destination by MARB. Either the transfer source or the
transfer destination can be selected as a block area (an area composed of a number of bytes or
words).
Table 8-11 summarizes register functions in block transfer mode.
Table 8-11 Register Functions in Block Transfer Mode
Register
Function
Initial Setting
Operation
23
0
MARA
Source address
register
Start address of
transfer source
Incremented/decremented
every transfer, or fixed
23
0
MARB
Destination
address register
Start address of
transfer destination
Incremented/decremented
every transfer, or fixed
0
ETCRAH
7
0
ETCRAL
7
Holds block
size
Block size
counter
Block size
Block size
Fixed
Decremented every
transfer; ETCRH value
copied when count reaches
H'00
15
0
ETCRB
Block transfer
counter
Number of block
transfers
Decremented every block
transfer; transfer ends
when count reaches
H'0000
Legend
MARA : Memory address register A
MARB : Memory address register B
ETCRA : Transfer count register A
ETCRB : Transfer count register B
MARA and MARB specify the start addresses of the transfer source and transfer destination,
respectively, as 24 bits. MAR can be incremented or decremented by 1 or 2 each time a byte or
word is transferred, or can be fixed.
Incrementing, decrementing, or holding a fixed value can be set separately for MARA and
MARB.
Содержание H8S/2631
Страница 28: ...xviii Appendix G Package Dimensions 1154 ...
Страница 341: ...316 Transfer SAR or DAR DAR or SAR Block area First block Nth block Figure 9 8 Memory Mapping in Block Transfer Mode ...
Страница 918: ...905 ø DREQ0 DREQ1 tDRQS tDRQH Figure 25 19 DMAC DREQ Input Timing ...
Страница 955: ...943 A 2 Instruction Codes Table A 2 shows the instruction codes ...