H8S-2350 RENESAS [Renesas Technology Corp], H8S-2350 Datasheet - Page 221

• Manufacturer Part Number: H8S-2350
• Description: 16-Bit Single-Chip Microcomputer
• Manufacturer: RENESAS [Renesas Technology Corp]

6.9
The H8S/2350 Group 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.
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
Rev. 3.00 Sep 15, 2006 page 187 of 988
T
W
Internal I/O register address
T
W
Section 6 Bus Controller
REJ09B0330-0300
T
3