147
T
p
1
T
p
2
T
r
T
c
1
T
c
2
Row address
Column address
CK
A21–A0
RAS
CAS
Figure 8.19 Precharge Timing (Long Pitch)
Control of Insertion of Wait States Using the
WAIT
Pin Input Signal: The number of wait
states inserted into the DRAM access cycle can be controlled by setting WCR1 and WCR2. When
the corresponding bits in WCR1 and WCR2 are cleared to 0, the column address output cycle ends
in 1 state and no wait states are inserted. When the bit is 1, the
WAIT
pin input signal is sampled
on the rise of the system clock (CK) directly preceding the second state of the column address
output cycle and the wait state is inserted as long as the level is low. When a high level is detected,
it shifts to the second state. Figure 8.20 shows the wait state timing in a long pitch bus cycle.
T
p
T
r
T
c
1
T
cw
(wait state)
T
c
2
Row address
Column address
CK
A21–A0
RAS
CAS
WAIT
Figure 8.20 Wait State Timing during DRAM Access (Long Pitch)
When the RW1 bit is set to 1, the number of wait states selected by CBR refresh wait state
insertion bits 1 and 0 (RLW1, RLW0) in the refresh control register (RCR) are inserted into the
CAS-before-RAS refresh cycle.
Summary of Contents for HD6417032
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Page 525: ...490 CK RAS CAS TRp TRc TRcc tRASD1 tRASD2 tCASD3 tCASD2 TRr tCSR Figure 20 18 Self Refresh ...
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