Rev. 2.00, 09/03, page 231 of 690
Tpw
Tp
Trr
Trc
Trc
Tmw
Hi-Z
Tnop
Trc
Trr
Trc
REF
REF
MRS
PALL
Notes: 1. Address pin to be connected to the A10 pin of SDRAM.
2. xx is UU, UL, LU, or LL.
3. The waveform for DACKn is when active low is specified.
CKIO
A25 to A0
CSn
RD/
WR
RASU/L
DQMxx
*
2
D31 to D0
BS
DACKn
*
3
A12/A11
*
1
CASU/L
Figure 7.29 Synchronous DRAM Mode Write Timing (Based on JEDEC)
7.9
Burst ROM Interface
The burst ROM interface is provided to access ROM that has the page mode function, such as
flash memory, in high speed. Basically the access to the ROM is performed in the same way as for
normal space. When the first cycle is terminated, however, negation of the
RD signal is not
executed. The accesses after the 2nd access are performed by exchanging only the address. In the
accesses after the 2nd access, the address is changed at the falling edge of CKIO.
The number of wait cycles specified by the W[3:0] bits in CSnWCR are inserted for the first
access cycle. The number of wait cycles specified by the BW[1:0] bits in CSnWCR are inserted
for the second and subsequent access cycles.
In the access to the burst ROM, the
BS signal is asserted only to the first access cycle. An external
wait input is valid only to the first access cycle. In the single access or write access that do not
perform the burst operation in the burst ROM interface, access timing is same as a normal space.
Table 7.18 lists a relationship between bus width, access size, and the number of bursts. Figure
7.30 shows a timing chart.
Summary of Contents for SH7705
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