AS7C331MFT18A
®
Signal descriptions
Signal I/O Properties
Description
CLK
I
I
CLOCK Clock. All inputs except OE, ZZ, and LBO are synchronous to this clock.
A,A0,A1
SYNC
SYNC
Address. Sampled when all chip enables are active and when ADSC or ADSP are asserted.
Data. Driven as output when the chip is enabled and when OE is active.
DQ[a,b] I/O
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
I
SYNC
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
ADSC
ADV
I
I
I
SYNC
SYNC
SYNC
Address strobe processor. Asserted LOW to load a new bus address or to enter standby mode.
Address strobe controller. Asserted LOW to load a new address or to enter standby mode.
Advance. Asserted LOW to continue burst read/write.
Global write enable. Asserted LOW to write all 32/36 and 18 bits. When HIGH, BWE and
BW[a,b] control write enable.
GWE
BWE
I
I
SYNC
SYNC
Byte write enable. Asserted LOW with GWE HIGH to enable effect of BW[a,b] inputs.
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 inactive, the cycle is a read cycle.
BW[a,b]
I
SYNC
Asynchronous output enable. I/O pins are driven when OE is active and the chip is in read
mode.
OE
I
I
ASYNC
STATIC
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.
LBO
ZZ
I
-
ASYNC Sleep. Places device in low power mode; data is retained. Connect to GND if unused.
No connect
NC
-
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.
1/21/05, v 1.4
Alliance Semiconductor
5 of 19
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
