M68AW128ML datasheet(9/20 Pages) STMICROELECTRONICS

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M68AW128ML

OPERATION

The M68AW128ML has a Chip Enable power

down feature which invokes an automatic standby

mode whenever either Chip Enable is de-asserted

(E = High) or LB and UB are de-asserted (LB and

UB = High). An Output Enable (G) signal provides

a high speed tri-state control, allowing fast read/

write cycles to be achieved with the common I/O

data bus. Operational modes are determined by

device control inputs W, E, LB and UB as summa-

rized in the Operating Modes table (see Table 6).

Table 6. Operating Modes

Note: 1. X = VIH or VIL.

Read Mode

The M68AW128ML is in the Read mode whenever

Write Enable (W) is High with Output Enable (G)

Low, and Chip Enable (E) is asserted. This pro-

vides access to data from eight or sixteen, de-

pending on the status of the signal UB and LB, of

the 2,097,152 locations in the static memory array,

specified by the 17 address inputs. Valid data will

be available at the eight or sixteen output pins

within tAVQV after the last stable address, provid-

ing G is Low and E is Low. If Chip Enable or Output

Enable access times are not met, data access will

be measured from the limiting parameter (tELQV,

tGLQV or tBLQV) rather than the address. Data out

may be indeterminate at tELQX,tGLQX and tBLQX

but data lines will always be valid at tAVQV.

Figure 8. Address Controlled, Read Mode AC Waveforms

Note: E = Low, G = Low, W = High, UB = Low and/or LB = Low.

Operation

DQ0-DQ7

DQ8-DQ15

Power

Deselected

VIH

Hi-Z

Standby (ISB)

Deselected

VIH

Hi-Z

Standby (ISB)

Lower Byte Read

VIL

VIH

VIL

VIH

Data Output

Hi-Z

Active (ICC)

Lower Byte Write

VIL

VIH

Data Input

Hi-Z

Active (ICC)

Output Disabled

VIL

VIH

Hi-Z

Active (ICC)

Upper Byte Read

VIL

VIH

VIL

VIH

VIL

Hi-Z

Data Output

Active (ICC)

Upper Byte Write

VIL

XVIH

VIL

Hi-Z

Data Input

Active (ICC)

Word Read

VIL

VIH

VIL

Data Output

Active (ICC)

Word Write

VIL

XVIL

VIL

Data Input

Active (ICC)

AI04839

tAVAV

tAVQV

tAXQX

A0-A16

DQ0-DQ7 and/or DQ8-DQ15

VALID

DATA VALID

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