248
8.5.4
Repeat Mode
Repeat mode can be specified by setting the RPE bit in DMACR to 1, and clearing the DTIE bit to
0. In repeat mode, MAR is updated after each byte or word transfer in response to a single transfer
request, and this is executed the number of times specified in ETCR. On completion of the
specified number of transfers, MAR and ETCRL are automatically restored to their original
settings and operation continues.
One address is specified by MAR, and the other by IOAR. The transfer direction can be specified
by the DTDIR bit in DMACR.
Table 8-8 summarizes register functions in repeat mode.
Table 8-8
Register Functions in Repeat Mode
Function
Register
DTDIR = 0 DTDIR = 1 Initial Setting
Operation
23
0
MAR
Source
address
register
Destination
address
register
Start address of
transfer destination
or transfer source
Incremented/
decremented every
transfer. Initial
setting is restored
when value reaches
H'0000
23
0
IOAR
15
H'FF
Destination
address
register
Source
address
register
Start address of
transfer source or
transfer destination
Fixed
0
ETCRH
7
0
ETCRL
7
Holds number of
transfers
Transfer counter
Number of transfers
Number of transfers
Fixed
Decremented every
transfer. Loaded with
ETCRH value when
count reaches H'00
Legend
MAR
: Memory address register
IOAR : I/O address register
ETCR : Transfer count register
DTDIR : Data transfer direction bit
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 ...