CY7C1541V18, CY7C1556V18
CY7C1543V18, CY7C1545V18
Document Number: 001-05389 Rev. *F
Page 10 of 28
The truth table for CY7C1541V18, CY7C1556V18, CY7C1543V18, and CY7C1545V18 follows.
[3, 4, 5, 6, 7, 8]
Truth Table
Operation
K
RPS WPS
DQ
DQ
DQ
DQ
Write Cycle:
Load address on the rising
edge of K; input write data
on two consecutive K and
K rising edges.
L-H
H
[9]
L
[10]
D(A) at K(t + 1)
↑
D(A + 1) at K(t +1)
↑
D(A + 2) at K(t + 2)
↑
D(A + 3) at K(t + 2)
↑
Read Cycle:
(2.0 cycle Latency)
Load address on the rising
edge of K; wait two cycles;
read data on two consec-
utive K and K rising edges.
L-H
L
[10]
X
Q(A) at K(t + 2)
↑
Q(A + 1) at K(t + 2)
↑
Q(A + 2) at K(t + 3)
↑
Q(A + 3) at K(t + 3)
↑
NOP: No Operation
L-H
H
H
D = X
Q = High-Z
D = X
Q = High-Z
D = X
Q = High-Z
D = X
Q = High-Z
Standby: Clock Stopped
Stopped X
X
Previous State
Previous State
Previous State
Previous State
The write cycle description table for CY7C1541V18 and CY7C1543V18 follows.
[3, 11]
Write Cycle Descriptions
BWS
0
/
NWS
0
BWS
1
/
NWS
1
K
K
Comments
L
L
L–H
–
During the data portion of a write sequence
:
CY7C1541V18
−
both nibbles (D
[7:0]
) are written into the device,
CY7C1543V18
−
both bytes (D
[17:0]
) are written into the device.
L
L
–
L-H During the data portion of a write sequence
:
CY7C1541V18
−
both nibbles (D
[7:0]
) are written into the device,
CY7C1543V18
−
both bytes (D
[17:0]
) are written into the device.
L
H
L–H
–
During the data portion of a write sequence
:
CY7C1541V18
−
only the lower nibble (D
[3:0]
) is written into the device, D
[7:4]
remains unaltered.
CY7C1543V18
−
only the lower byte (D
[8:0]
) is written into the device, D
[17:9]
remains unaltered.
L
H
–
L–H During the data portion of a write sequence
:
CY7C1541V18
−
only the lower nibble (D
[3:0]
) is written into the device, D
[7:4]
remains unaltered.
CY7C1543V18
−
only the lower byte (D
[8:0]
) is written into the device, D
[17:9]
remains unaltered.
H
L
L–H
–
During the data portion of a write sequence
:
CY7C1541V18
−
only the upper nibble (D
[7:4]
) is written into the device, D
[3:0]
remains unaltered.
CY7C1543V18
−
only the upper byte (D
[17:9]
) is written into the device, D
[8:0]
remains unaltered.
H
L
–
L–H During the data portion of a write sequence
:
CY7C1541V18
−
only the upper nibble (D
[7:4]
) is written into the device, D
[3:0]
remains unaltered.
CY7C1543V18
−
only the upper byte (D
[17:9]
) is written into the device, D
[8:0]
remains unaltered.
H
H
L–H
–
No data is written into the devices during this portion of a write operation.
H
H
–
L–H No data is written into the devices during this portion of a write operation.
Notes
3. X = “Don't Care,” H = Logic HIGH, L = Logic LOW,
↑
represents rising edge.
4. Device powers up deselected with the outputs in a tri-state condition.
5. “A” represents address location latched by the devices when transaction was initiated. A + 1, A + 2, and A + 3 represents the address sequence in the burst.
6. “t” represents the cycle at which a read/write operation is started. t + 1, t + 2, and t + 3 are the first, second and third clock cycles respectively succeeding the “t” clock cycle.
7. Data inputs are registered at K and K rising edges. Data outputs are delivered on K and K rising edges, also.
8. It is recommended that K = K = HIGH when clock is stopped. This is not essential, but permits most rapid restart by overcoming transmission line charging symmetrically.
9. If this signal was LOW to initiate the previous cycle, this signal becomes a “Don’t Care” for this operation.
10. This signal was HIGH on previous K clock rise. Initiating consecutive read or write operations on consecutive K clock rises is not permitted. The device ignores the
second read or write request.
11. Is based on a write cycle was initiated per the
The write cycle description table for CY7C1541V18 and CY7C1543V18 follows.
[3, 11]
table. NWS
0
, NWS
1
, BWS
0
, BWS
1
,
BWS
2
,
and BWS
3
can be altered on different portions of a write cycle, as long as the setup and hold requirements are achieved.
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