connection to all devices in the array and connected to
the READ line from the system control bus. This as-
sures that all deselected memory devices are in their
low-power standby mode and that the output pins are
only active when data is desired from a particular mem-
ory device.
System Applications
During the switch between active and standby condi-
tions, transient current peaks are produced on the ris-
ing and falling edges of Chip Enable. The magnitude of
these transient current peaks is dependent on the out-
put capacitance loading of the device. At a minimum, a
0.1 µF ceramic capacitor (high frequency, low inherent
inductance) should be used on each device between
V
CC
and V
SS
to minimize transient effects. In addition,
to overcome the voltage drop caused by the inductive
effects of the printed circuit board traces on EPROM ar-
rays, a 4.7 µF bulk electrolytic capacitor should be used
between V
CC
and V
SS
for each eight devices. The loca-
tion of the capacitor should be close to where the
power supply is connected to the array.
MODE SELECT TABLE
Mode
Read
Output Disable
Standby (TTL)
Standby (CMOS)
Program
Program Verify
Program Inhibit
Autoselect
(Note 3)
Manufacturer Code
Device Code
CE#
V
IL
X
V
IH
V
CC
±
0.3 V
V
IL
V
IL
V
IH
V
IL
V
IL
OE#
V
IL
V
IH
X
X
X
V
IL
V
IH
V
IL
V
IL
A0
X
X
X
X
X
X
X
V
IL
V
IH
A9
X
X
X
X
X
X
X
V
H
V
H
V
PP
X
X
X
X
V
PP
V
PP
V
PP
X
X
Outputs
D
OUT
High Z
High Z
High Z
D
IN
D
OUT
High Z
01h
10h
Notes:
1. V
H
= 12.0 V
±
0.5 V.
2. X = Either V
IH
or V
IL
.
3. A1–A8 and A10–14 = V
IL
4. See DC Programming Characteristics for V
PP
voltage during programming.
6
Am27C256
AMD [ ADVANCED MICRO DEVICES ]
