®
AS7C33128FT18B
12/10/04; v.1.3 Alliance Semiconductor P. 5 of 19
Signal descriptions
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 guara nteed after the time tZZI is met. After entering SNOO ZE 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 com-
plete. 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.
Pin I/O Properties Description
CLK I CLOCK Clock. All inputs except OE, ZZ , and LBO are synchronous to this clock.
A,A0,A1 I SYNC Address. Sampled when all chip enable s are active and when ADSC or ADSP are asserted.
DQ[a,b] I/O SYNC Data. Driven as output when the chip is enabled and when OE is active.
CE0 I SYNC 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.
CE1, CE2 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.
ADSP I SYNC Address strobe processor. Asserted low to load a new address or to enter stan dby mode.
ADSC I SYNC Address strobe controller. Asserted low to load a new address or to enter standby mode.
ADV I SYNC Advance. Asserted low to continue burst read/write.
GWE I SYNC Global write enable. Asserted low to write all 18 bits. When high , BWE and BW[a,b] control write
enable.
BWE I SYNC Byte write enable. Asserted low with GWE high to enable ef fect of BW[a,b] inputs.
BW[a,b] I SYNC Write enables. Used to control write of individual bytes when GWE is high and BWE is 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 in ac tive,
the cycle is a read cycle.
OE I ASYNC Asynchronous output enable. I/O pins are driven when OE is active and chip is in read mode.
LBO ISTATIC
Selects Burst mode. When tied to VDD or left floating, device follows interleaved Burst order. When
driven Low, device follows linear Burst order. This signal is internally pulled High.
ZZ I ASYNC Snooze. Places device in low power mode; data is retained. Connect to GND if unused.
NC - - No connect