7C1325B-100 データシートの表示（PDF） - Cypress Semiconductor
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7C1325B-100 Datasheet PDF : 17 Pages
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CY7C1325B
I/Os must be three-stated prior to the presentation of data to
DQ[15:0] and DP[1:0]. As a safety precaution, the data lines are
three-stated once a write cycle is detected, regardless of the
state of OE.
Single Write Accesses Initiated by ADSC
This write access is initiated when the following conditions are
satisfied at clock rise: (1) CE1, CE2, and CE3 are all asserted
active, (2) ADSC is asserted LOW, (3) ADSP is deasserted
HIGH, and (4) the write input signals (GW, BWE, and BWS[1:0])
indicate a write access. ADSC is ignored if ADSP is active LOW.
The addresses presented are loaded into the address register,
burst counter/control logic and delivered to the RAM core. The
information presented to DQ[15:0] and DP[1:0] will be written
into the specified address location. Byte writes are allowed,
with BWS0 controlling DQ[7:0] and DP0 while BWS1 controlling
DQ[15:8] and DP1. All I/Os are three-stated when a write is
detected, even a byte write. Since these are common I/O de-
vices, the asynchronous OE input signal must be deasserted
and the I/Os must be three-stated prior to the presentation of
data to DQ[15:0] and DP[1:0]. As a safety precaution, the data
lines are three-stated once a write cycle is detected, regard-
less of the state of OE.
Burst Sequences
This family of devices provides a 2-bit wrap-around burst
counter inside the SRAM. The burst counter is fed by A[1:0],
and can follow either a linear or interleaved burst order. The
burst order is determined by the state of the MODE input. A
LOW on MODE will select a linear burst sequence. A HIGH on
MODE will select an interleaved burst order. Leaving MODE
unconnected will cause the device to default to an interleaved
burst sequence.
Table 1. Counter Implementation for the Intel®
Pentium®/80486 Processor’s Sequence
First
Address
AX + 1, Ax
00
01
10
11
Second
Address
AX + 1, Ax
01
00
11
10
Third
Address
AX + 1, Ax
10
11
00
01
Fourth
Address
AX + 1, Ax
11
10
01
00
Table 2. Counter Implementation for a Linear Sequence
First
Address
AX + 1, Ax
00
01
10
11
Second
Address
AX + 1, Ax
01
10
11
00
Third
Address
AX + 1, Ax
10
11
00
01
Fourth
Address
AX + 1, Ax
11
00
01
10
Sleep Mode
The ZZ input pin is an asynchronous input. Asserting ZZ HIGH
places the SRAM in a power conservation “sleep” mode. Two
clock cycles are required to enter into or exit from this “sleep”
mode. While in this mode, data integrity is guaranteed. Ac-
cesses pending when entering the “sleep” mode are not con-
sidered valid nor is the completion of the operation guaran-
teed. The device must be deselected prior to entering the
“sleep” mode. CE1, CE2, CE3, ADSP, and ADSC must remain
inactive for the duration of tZZREC after the ZZ input returns
LOW.
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