HD6412373R RENESAS [Renesas Technology Corp], HD6412373R Datasheet - Page 336

• Manufacturer Part Number: HD6412373R
• Description: Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2300 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 6 Bus Controller (BSC)
6.9.2
Table 6.12 shows the pin states in an idle cycle.
Table 6.12 Pin States in Idle Cycle
Pins
A23 to A0
D15 to D0
CSn (n = 7 to 0)
UCAS, LCAS
AS
RD
(OE)
HWR, LWR
DACKn (n = 1, 0)
EDACKn (n = 3, 2)
Notes: 1. Remains low in DRAM space RAS down mode.
6.10
This LSI has a write data buffer function for 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
to 1 in BCR.
Figure 6.83 shows an example of the timing when the write data buffer function is used. When this
function is used, if an external address space write or DMA single address mode transfer continues
for two states or longer, and there is an internal access next, an external write only 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 address space write rather than waiting
until it ends.
Rev.7.00 Mar. 18, 2009 page 268 of 1136
REJ09B0109-0700
2. Remains low in a DRAM space refresh cycle.
Pin States in Idle Cycle
Write Data Buffer Function
Pin State
Contents of following bus cycle
High impedance
High *
High *
High
High
High
High
High
High
1
2
*
2