Cypress CY7C1550V18, CY7C1548V18 Write Cycle Descriptions, Operation, BWS0 BWS1, Comments, NWS1

CY7C1546V18, CY7C1557V18

CY7C1548V18, CY7C1550V18

Truth Table

The truth table for CY7C1546V18, CY7C1557V18, CY7C1548V18, and CY7C1550V18 follows. [3, 4, 5, 6, 7, 8]

Operation					K	LD	R/W	DQ	DQ
Write Cycle:					L-H	L	L	D(A) at K(t + 1) ↑	D(A+1) at
										K(t + 1) ↑
Load address; wait one cycle;
input write data on consecutive K and			K	rising edges.
Read Cycle: (2.0 cycle Latency)					L-H	L	H	Q(A) at K(t + 2) ↑	Q(A+1) at
											K(t + 2) ↑
Load address; wait two cycle;
read data on consecutive K and	K	rising edges.
NOP: No Operation					L-H	H	X	High Z	High Z
Standby: Clock Stopped					Stopped	X	X	Previous State	Previous State

Write Cycle Descriptions

The write cycle description table for CY7C1546V18 and CY7C1548V18 follows. [3, 9]

BWS0/	BWS1/		K			Comments
					K
NWS0		NWS1
L		L	L–H		–	During the data portion of a write sequence:
						CY7C1546V18 − both nibbles (D[7:0]) are written into the device.
						CY7C1548V18 − both bytes (D[17:0]) are written into the device.
L		L	–	L-H		During the data portion of a write sequence:
						CY7C1546V18 − both nibbles (D[7:0]) are written into the device.
						CY7C1548V18 − both bytes (D[17:0]) are written into the device.
L		H	L–H		–	During the data portion of a write sequence:
						CY7C1546V18 − only the lower nibble (D[3:0]) is written into the device, D[7:4]		remains unaltered.
						CY7C1548V18 − 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:
						CY7C1546V18 − only the lower nibble (D[3:0]) is written into the device, D[7:4]		remains unaltered.
						CY7C1548V18 − 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:
						CY7C1546V18 − only the upper nibble (D[7:4]) is written into the device, D[3:0]		remains unaltered.
						CY7C1548V18 − 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:
						CY7C1546V18 − only the upper nibble (D[7:4]) is written into the device, D[3:0]		remains unaltered.
						CY7C1548V18 − 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 represents the address sequence in the burst.

6.“t” represents the cycle at which a read/write operation is started. t + 1 and t + 2 are the first and second clock cycles 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.

8.Cypress recommends that K = K = HIGH when clock is stopped. This is not essential but permits most rapid restart by overcoming transmission line charging symmetrically.

9.Is based on a write cycle is initiated as per the Write Cycle Descriptions table. NWS0, NWS1, BWS0, BWS1, BWS2, and BWS3 is altered on different portions of a write cycle, as long as the setup and hold requirements are met.

Document Number: 001-06550 Rev. *E Page 10 of 28

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