M68AW512M
8/18
OPERATION
The M68AW512M 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 = V
IH
or V
IL
.
Read Mode
The M68AW512M 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 8,388,608 locations in the static memory array,
specified by the 19 address inputs. Valid data will
be available at the eight or sixteen output pins
within t
AVQV
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 (t
ELQV
,
t
GLQV
or t
BLQV
) rather than the address. Data out
may be indeterminate at t
ELQX
, t
GLQX
and t
BLQX
but data lines will always be valid at t
AVQV
.
Figure 7. Address Controlled, Read Mode AC Waveforms
Note: E = Low, G = Low, W = High, UB = Low and/or LB = Low.
Operation E W G LB UB DQ0-DQ7 DQ8-DQ15 Power
Deselected
V
IH
XXXX Hi-Z Hi-Z
Standby (I
SB
)
Deselected X X X
V
IH
V
IH
Hi-Z Hi-Z
Standby (I
SB
)
Lower Byte Read
V
IL
V
IH
V
IL
V
IL
V
IH
Data Output Hi-Z
Active (I
CC
)
Lower Byte Write
V
IL
V
IL
X
V
IL
V
IH
Data Input Hi-Z
Active (I
CC
)
Output Disabled
V
IL
V
IH
V
IH
X X Hi-Z Hi-Z
Active (I
CC
)
Upper Byte Read
V
IL
V
IH
V
IL
V
IH
V
IL
Hi-Z Data Output
Active (I
CC
)
Upper Byte Write
V
IL
V
IL
X
V
IH
V
IL
Hi-Z Data Input
Active (I
CC
)
Word Read
V
IL
V
IH
V
IL
V
IL
V
IL
Data Output Data Output
Active (I
CC
)
Word Write
V
IL
V
IL
X
V
IL
V
IL
Data Input Data Input
Active (I
CC
)
AI05839
tAVAV
tAVQV tAXQX
A0-A18
DQ0-DQ7 and/or DQ8-DQ15
VALID
DATA VALID
