285
8.5.14
Relation Between External Bus Requests, Refresh Cycles, the DTC, and the DMAC
There can be no break between a DMA cycle read and a DMA cycle write. This means that a
refresh cycle, external bus release cycle, or DTC cycle is not generated between the external read
and external write in a DMA cycle.
In the case of successive read and write cycles, such as in burst transfer or block transfer, a refresh
or external bus released state may be inserted after a write cycle. Since the DTC has a lower
priority than the DMAC, the DTC does not operate until the DMAC releases the bus.
When DMA cycle reads or writes are accesses to on-chip memory or internal I/O registers, these
DMA cycles can be executed at the same time as refresh cycles or external bus release. However,
simultaneous operation may not be possible when a write buffer is used.
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 ...