AM27C256-120EC AMD [Advanced Micro Devices], AM27C256-120EC Datasheet - Page 7

• Manufacturer Part Number: AM27C256-120EC
• Description: 256 Kilobit (32,768 x 8-Bit) CMOS EPROM
• Manufacturer: AMD [Advanced Micro Devices]

Output OR-Tieing
To accommodate multiple memory connections, a two-
line control function is provided to allow for:
It is recommended that CE be decoded and used as the
primary device-selecting function, while OE be made a
common connection to all devices in the array and con-
nected to the READ line from the system control bus.
This assures that all deselected memory devices are in
low-power standby mode and that the output pins are
only active when data is desired from a particular
memory device.
MODE SELECT TABLE
2-38
Notes:
1. V H = 12.0 V + 0.5 V
2. X = Either V
3. A1–A8 = A10–A14 = V
4. See DC Programming Characteristics for V
Mode
Read
Output Disable
Standby (TTL)
Standby (CMOS)
Program
Program Verify
Program Inhibit
Low memory power dissipation
Assurance that output bus contention will not occur
Auto Select
AMD
(Note 3)
IH
or V
Manufacturer
Code
Device Code
IL
IL
Pins
V
CC
PP
CE
V
V
V
V
V
V
V
+ 0.3 V
X
IH
IH
IH
IL
IL
IL
IL
voltage during programming.
Am27C256
OE
V
V
V
V
V
V
V
X
X
IH
IH
IH
IL
IL
IL
IL
System Applications
During the switch between active and standby condi-
tions, transient current peaks are produced on the rising
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- F ceramic capacitor (high frequency, low inherent
inductance) should be used on each device between
V
overcome the voltage drop caused by the inductive ef-
fects of the printed circuit board traces on EPROM ar-
rays, a 4.7- F bulk electrolytic capacitor should be used
between V
tion of the capacitor should be close to where the power
supply is connected to the array.
CC
and V
V
A0
V
X
X
X
X
X
X
X
IH
IL
SS
CC
to minimize transient effects. In addition, to
and V
SS
A9
V
V
X
X
X
X
X
X
X
H
H
for each eight devices. The loca-
VPP
VPP
VPP
VPP
X
X
X
X
X
X
Outputs
High-Z
High-Z
High-Z
High-Z
D
D
01H
10H
D
OUT
OUT
IN