AS7C33256PFD18B
®
Signal descriptions
Signal
CLK
I/O
Properties
CLOCK
Description
I
Clock. All inputs except OE, ZZ, LBO are synchronous to this clock.
Address. Sampled when all chip enables are active and ADSC or ADSP are
asserted.
A,A0,A1
DQ[a,b]
I
SYNC
I/O SYNC
Data. Driven as output when the chip is enabled and OE is active.
Master chip enable. Sampled on clock edges when ADSP or ADSC is active.
When CE0 is inactive, ADSP is blocked. Refer to the Synchronous Truth Table for
more information.
CE0
I
SYNC
Synchronous chip enables. Active HIGH and active LOW, respectively. Sampled
on clock edges when ADSC is active or when CE0 and ADSP are active.
CE1, CE2
ADSP
I
I
SYNC
SYNC
Address strobe (processor). Asserted LOW to load a new address or to enter
standby mode.
Address strobe (controller). Asserted LOW to load a new address or to enter
standby mode.
ADSC
ADV
GWE
I
I
I
SYNC
SYNC
SYNC
Burst advance. Asserted LOW to continue burst read/write.
Global write enable. Asserted LOW to write all 18 bits. When HIGH, BWE and
BW[a,b] control write enable.
Byte write enable. Asserted LOW with GWE = HIGH to enable effect of BW[a,b]
inputs.
BWE
BW[a,b]
OE
I
I
I
I
SYNC
Write enables. Used to control write of individual bytes when GWE = HIGH and
BWE = LOW. If any of BW[a,b] is active with GWE = HIGH and BWE = LOW
the cycle is a write cycle. If all BW[a,b] are inactive, the cycle is a read cycle.
SYNC
Asynchronous output enable. I/O pins are driven when OE is active and the chip is
in read mode.
ASYNC
STATIC
Selects Burst mode. When tied to V or left floating, device follows interleaved
DD
LBO
Burst order. When driven Low, device follows linear Burst order. This signal is
internally pulled High.
Snooze. Places device in low power mode; data is retained. Connect to GND if
unused.
ZZ
I
-
ASYNC
-
NC
No connect
Snooze Mode
SNOOZE MODE is a low current, power-down mode in which the device is deselected and current is reduced to ISB2. The duration of
SNOOZE MODE is dictated by the length of time the ZZ is in a High state.
The ZZ pin is an asynchronous, active high input that causes the device to enter SNOOZE MODE.
When the ZZ pin becomes a logic High, ISB2 is guaranteed after the time tZZI is met. After entering SNOOZE MODE, all inputs except ZZ
is disabled and all outputs go to High-Z. Any operation pending when entering SNOOZE MODE is not guaranteed to successfully complete.
Therefore, SNOOZE MODE (READ or WRITE) must not be initiated until valid pending operations are completed. Similarly, when exiting
SNOOZE MODE during tPUS, only a DESELECT or READ cycle should be given while the SRAM is transitioning out of SNOOZE
MODE.
1/31/05; v.1.2
Alliance Semiconductor
P. 5 of 19
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
