267
8.5.9
Basic DMAC Bus Cycles
An example of the basic DMAC bus cycle timing is shown in figure 8-18. In this example, word-
size transfer is performed from 16-bit , 2-state access space to 8-bit, 3-state access space. When
the bus is transferred from the CPU to the DMAC, a source address read and destination address
write are performed. The bus is not released in response to another bus request, etc., between
these read and write operations. As with CPU cycles, DMA cycles conform to the bus controller
settings.
ø
Address bus
DMAC cycle (1-word transfer)
RD
LWR
HWR
Source
address
Destination address
CPU cycle
CPU cycle
T
1
T
2
T
3
T
1
T
2
T
3
T
1
T
2
Figure 8-18 Example of DMA Transfer Bus Timing
The address is not output to the external address bus in an access to on-chip memory or an internal
I/O register.
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 ...