AMD27C64 Datasheet, PDF (6/11 Pages) Advanced Micro Devices – 64 Kilobit (8,192 x 8-Bit) CMOS EPROM

Output OR-Tieing
To accommodate multiple memory connections, a two-
line control function is provided to allow for:
s Low memory power dissipation
s Assurance that output bus contention will not occur
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.
AMD
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-µF ceramic capacitor (high frequency, low inherent
inductance) should be used on each device between
VCC and VSS to minimize transient effects. In addition, to
overcome the voltage drop caused by the inductive ef-
fects of the printed circuit board traces on EPROM ar-
rays, a 4.7-µF bulk electrolytic capacitor should be used
between VCC and VSS 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
Pins
CE
VIL
OE
PGM
A0
A9
VPP
VIL
X
X
X
X
Output Disable
X
VIH
X
X
X
X
Standby (TTL)
VIH
X
X
X
X
X
Standby (CMOS)
VCC ± 0.3 V
X
X
X
X
X
Program
VIL
X
VIL
X
X
VPP
Program Verify
VIL
VIL
VIH
X
X
VPP
Program Inhibit
VIH
X
X
X
X
VPP
Manufacturer
Auto Select
Code
VIL
(Note 3)
Device Code
VIL
VIL
X
VIL
VH
X
VIL
X
VIH
VH
X
Notes:
1. VH = 12.0 V ± 0.5 V
2. X = Either VIH or VIL
3. A1–A8 = A10–A12 = VIL
4. See DC Programming Characteristics for VPP voltage during programming.
Outputs
DOUT
High-Z
High-Z
High-Z
DIN
DOUT
High-Z
01H
15H
Am27C64
2-15