153
The high-level duty of the
CAS
signal can be selected in short-pitch, high-speed page mode
using the CAS duty bit (CDTY) in DCR. When the CDTY bit is cleared to 0, the high-level
duty is 50% of the T
C
state; when CDTY is set to 1, it is 35% of the T
C
state.
•
Long-pitch, high-speed page mode: When the RW1, WW1, DRW1, and DWW1 bits in WCR1
and WCR2 are set to 1, and the corresponding DRAM access cycle is continuing, the
CAS
signal and column address output cycles (2 states) continue as long as the row addresses
continue to match. When the
WAIT
signal is detected at the low level, the second cycle of the
column address output cycle is repeated as the wait state. Figure 8.26 shows the timing for
long-pitch, high-speed page mode. See sections 20.1.3 (3) and 20.2.3 (3), Bus Timing, for
more information about the timing.
T
p
T
r
T
c
1
T
c
2
CK
A21–AD0
RAS
CAS
Column address 1
Data 1
WR
AD15–AD0
Column address 2
T
c
1
T
c
2
Data 2
Data 1
Data 2
Read
WR
AD15–AD0
Write
Row address 1
Figure 8.26 Long-Pitch, High-Speed Page Mode (Read/Write Cycle)
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