M27128A-20F6 STMICROELECTRONICS [STMicroelectronics], M27128A-20F6 Datasheet - Page 3

• Manufacturer Part Number: M27128A-20F6
• Description: NMOS 128K 16K x 8 UV EPROM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Table 3. Operating Modes
Note: X = V
DEVICE OPERATION (cont’d)
For the most efficient use of these two control lines,
E should be decoded and used as the primary
device selecting function, while G should be made
a common connection to all devices in the array
and connected to the READ line from the system
control bus.
This ensures that all deselected memory devices
are in their low power standby mode and that the
output pins are only active when data is required
from a particular memory device.
System Considerations
The power switching characteristics of fast
EPROMs require careful decoupling of the devices.
The supply current, I
are of interest to the system designer: the standby
current level, the active current level, and transient
current peaks that are produced by the falling and
rising edges of E. The magnitude of this transient
current peaks is dependent on the capacitive and
inductive loading of the device at the output. The
associated transient voltage peaks can be sup-
pressed by complying with the two line output
control and by properly selected decoupling ca-
pacitors. It is recommended that a 1 F ceramic
capacitor be used on every device between V
and V
Table 4. Electronic Signature
Manufacturer’s Code
Device Code
Read
Output Disable
Program
Verify
Program Inhibit
Standby
Electronic Signature
SS
Identifier
. This should be a high frequency capacitor
IH
Mode
or V
IL
, V
ID
= 12V
CC
, has three segments that
V
A0
V
0.5%.
IH
IL
V
V
V
V
V
V
V
E
IH
IH
Q7
IL
IL
IL
IL
IL
0
1
Q6
0
0
V
V
V
V
V
G
X
X
IH
IH
IL
IL
IL
CC
Q5
1
0
V
of low inherent inductance and should be placed
as close to the device as possible. In addition, a
4.7 F bulk electrolytic capacitor should be used
between V
bulk capacitor should be located near the power
supply connection point. The purpose of the bulk
capacitor is to overcome the voltage drop caused
by the inductive effects of PCB traces.
Programming
When delivered (and after each erasure for UV
EPPROM), all bits of the M27128A are in the “1"
state. Data is introduced by selectively program-
ming ”0s" into the desired bit locations. Although
only “0s” will be programmed, both “1s” and “0s”
can be present in the data word. The only way to
change a “0" to a ”1" is by ultraviolet light erasure.
The M27128A is in the programming mode when
V
The data to be programmed is applied 8 bits in
parallel, to the data output pins. The levels required
for the address and data inputs are TTL.
Fast Programming Algorithm
Fast Programming Algorithm rapidly programs
M27128A EPROMs using an efficient and reliable
method suited to the production programming en-
vironment. Programming reliability is also ensured
as the incremental program margin of each byte is
Q4
IL
PP
0
0
V
V
V
V
Pulse
P
X
X
IH
IH
IH
IH
input is at 12.5V and E and P are at TTL low.
Q3
0
1
CC
and GND for every eight devices. The
V
A9
X
X
X
X
X
X
Q2
ID
0
0
Q1
0
0
V
V
V
V
V
V
V
V
CC
CC
CC
CC
PP
PP
PP
PP
Q0
0
1
Codes Out
M27128A
Data Out
Data Out
Hex Data
Q0 - Q7
Data In
Hi-Z
Hi-Z
Hi-Z
20h
89h
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