M27512-20F6 STMICROELECTRONICS [STMicroelectronics], M27512-20F6 Datasheet - Page 3

• Manufacturer Part Number: M27512-20F6
• Description: NMOS 512K 64K 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 GV
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 dese-
lected memory devices are in their low power
standby mode and that the output pins are only
active when data is required from a particular mem-
ory 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 the 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 recommenced that a 1 F ceramic
capacitor be used on every device between V
and 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
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
CC
and V
IL
, V
ID
= 12V
SS
CC
for every eight devices. The
, has three segments that
V
A0
V
0.5%.
IH
IL
V
Q7
IL
0
0
V
V
V
V
V
V
Pulse
E
IH
IH
IH
IL
IL
IL
PP
should be
Q6
0
0
CC
Q5
1
0
GV
V
V
V
V
V
V
X
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, all bits of
the M27512 are in the “1" state. Data is introduced
by selectively programming ”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 M27512 is in the programming
mode when GV
TTL-low. 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.
The M27512 can use PRESTO Programming Algo-
rithm that drastically reduces the programming
time (typically less than 50 seconds). Nevertheless
to achieve compatibility with all programming
equipment, the standard Fast Programming Algo-
rithm may also be used.
Fast Programming Algorithm
Fast Programming Algorithm rapidly programs
M27512 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
continually monitored to determine when it has
been successfully programmed. A flowchart of the
M27512 Fast Programming Algorithm is shown in
Figure 8.
PP
PP
IH
IL
IL
IL
PP
Q4
0
0
Q3
0
1
PP
Q2
0
1
V
A9
X
X
X
X
X
X
input is at 12.5V and E is at
ID
Q1
0
0
Q0
0
1
Data Out
Data Out
Q0 - Q7
Data In
Codes
Hi-Z
Hi-Z
Hi-Z
Hex Data
M27512
0Dh
20h
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