6.42
IDT71V2556, IDT71V2558, 128K x 36, 256K x 18, 3.3V Synchronous ZBT™ SRAMs
with 2.5V I/O, Burst Counter, and Pipelined Outputs Commercial and Industrial Temperature Ranges
9
Synchronous Truth Table
(1)
Partial Truth Table for Writes
(1)
NOTES:
1. L = VIL, H = VIH, X = Don’t Care.
2. When ADV/LD signal is sampled high, the internal burst counter is incremented. The R/W signal is ignored when the counter is advanced. Therefore the nature of
the burst cycle (Read or Write) is determined by the status of the R/W signal when the first address is loaded at the beginning of the burst cycle.
3. Deselect cycle is initiated when either (CE1, or CE2 is sampled high or CE2 is sampled low) and ADV/LD is sampled low at rising edge of clock. The data bus will
tri-state two cycles after deselect is initiated.
4. When CEN is sampled high at the rising edge of clock, that clock edge is blocked from propogating through the part. The state of all the internal registers and the I/
Os remains unchanged.
5. To select the chip requires CE1 = L, CE2 = L, CE2 = H on these chip enables. Chip is deselected if any one of the chip enables is false.
6. Device Outputs are ensured to be in High-Z after the first rising edge of clock upon power-up.
7. Q - Data read from the device, D - data written to the device.
NOTES:
1. L = VIL, H = VIH, X = Don’t Care.
2. Multiple bytes may be selected during the same cycle.
3. N/A for X18 configuration.
CEN
W
LD
BW
L L Select L Valid External X LOAD WRITE D
(7)
L H Select L X External X LOAD READ Q
(7)
L X X H Valid Internal LOAD WRITE /
BURST WRITE
BURST WRITE
(Advance burst counter)
(2)
D
(7)
L X X H X Internal LOAD READ /
BURST READ
BURST READ
(Advance burst counter)
(2)
Q
(7)
L X Deselect L X X X DESELECT or STOP
(3)
HiZ
L X X H X X DESELECT / NOOP NOOP HiZ
H X X X X X X SUSPEND
(4)
Previous Value
4875 tbl 08
W
BW
BW
BW
BW
READ HXXXX
WRITE ALL BYTES L L L L L
WRITE BYTE 1 (I/O[0:7], I/O
P1
)
(2)
LLHHH
WRITE BYTE 2 (I/O[8:15], I/O
P2
)
(2)
LHLHH
WRITE BYTE 3 (I/O[16:23], I/O
P3
)
(2,3)
LHHLH
WRITE BYTE 4 (I/O[24:31], I/O
P4
)
(2,3)
LHHHL
NO WRITE LHHHH
4875 tbl 09