HD6412350 Hitachi, HD6412350 Datasheet - Page 204

• Manufacturer Part Number: HD6412350
• Description: (HD6412350 / HD6432351) 16-BIT MICROCONTROLLER
• Manufacturer: Hitachi

6.9
The H8S/2350 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 transfers 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 6-36 shows an example of the timing when the write data buffer function is used. When
this function is used, if an external write or DMA single address mode transfer 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.
184
External
space
write
Internal address bus
Internal read signal
Figure 6-36 Example of Timing when Write Data Buffer Function is Used
Write Data Buffer Function
HWR, LWR
D
A
15
23
to D
to A
CSn
0
0
T
1
On-chip memory read Internal I/O register read
T
Internal memory
2
External write cycle
External address
T
W
Internal I/O register address
T
W
T
3