199
7.9
Write Data Buffer Function
The H8S/2633 Series has a write data buffer function in the external data bus. Using the write data
buffer function enables external writes and DMA single address mode transmission to be executed
in parallel with internal accesses. The write data buffer function is made available by setting the
WDBE bit in BCRL to 1.
Figure 7-38 shows an example of the timing when the write data buffer function is used. When
this function is used, if an external write and DMA single address mode transmission continues for
2 states or longer, and there is an internal access next, only an external write is executed in the first
state, but from the next state onward an internal access (on-chip memory or internal I/O register
read/write) is executed in parallel with the external write rather than waiting until it ends.
T
1
Internal address bus
A23 to A0
External write cycle
HWR
,
LWR
T
2
T
W
T
W
T
3
On-chip memory read
Internal I/O register read
CSn
Internal read signal
D15 to D0
External address
Internal memory
External
space
write
Internal I/O register address
Figure 7-38 Example of Timing when Write Data Buffer Function 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 ...