27C256-12/L Microchip Technology, 27C256-12/L Datasheet - Page 6

• Manufacturer Part Number: 27C256-12/L
• Description: IC OTP 256KBIT 120NS 32PLCC
• Manufacturer: Microchip Technology

Specifications of 27C256-12/L

• Format - Memory: EPROMs
• Memory Type: OTP EPROM
• Memory Size: 256K (32K x 8)
• Speed: 120ns
• Interface: Parallel
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 32-PLCC
• Lead Free Status / RoHS Status: Request inventory verification / Request inventory verification

27C256
1.3
The standby mode is defined when the CE pin is high
(VIH) and a program mode is not defined.
When these conditions are met, the supply current will
drop from 20 mA to 100 A.
1.4
This feature eliminates bus contention in multiple bus
microprocessor systems and the outputs go to a high
impedance when the following condition is true:
• The OE pin is high and the program mode is not
1.5
Windowed products offer the ability to erase the mem-
ory array. The memory matrix is erased to the all 1’s
state when exposed to ultraviolet light. To ensure com-
plete erasure, a dose of 15 watt-second/cm
required. This means that the device window must be
placed within one inch and directly underneath an ultra-
violet lamp with a wavelength of 2537 Angstroms,
intensity of 12,000 W/cm
utes.
1.6
The Express Algorithm has been developed to improve
on the programming throughput times in a production
environment. Up to ten 100-microsecond pulses are
applied until the byte is verified. No overprogramming
is required. A flowchart of the express algorithm is
shown in Figure 1-3.
Programming takes place when:
a)
b)
c)
d)
Since the erased state is “1” in the array, programming
of “0” is required. The address to be programmed is set
via pins A0-A14 and the data to be programmed is pre-
sented to pins O0-O7. When data and address are sta-
ble, a low going pulse on the CE line programs that
location.
DS11001N-page 6
defined.
V
V
the OE pin is high, and
the CE pin is low.
CC
PP
Standby Mode
Output Enable
Erase Mode (U.V. Windowed
Versions)
Programming Mode
is brought to the proper V
is brought to the proper voltage,
2
for approximately 20 min-
H
level,
2
is
1.7
After the array has been programmed it must be veri-
fied to ensure all the bits have been correctly pro-
grammed. This mode is entered when all the following
conditions are met:
a)
b)
c)
d)
1.8
When programming multiple devices in parallel with dif-
ferent data, only CE need be under separate control to
each device. By pulsing the CE line low on a particular
device, that device will be programmed; all other
devices with CE held high will not be programmed with
the data, although address and data will be available on
their input pins.
1.9
In this mode specific data is output which identifies the
manufacturer as Microchip Technology Inc. and device
type. This mode is entered when Pin A9 is taken to V
(11.5V to 12.5V). The CE and OE lines must be at V
A0 is used to access any of the two non-erasable bytes
whose data appears on O0 through O7.
Pin
Manufacturer
Device Type*
* Code subject to change
Identity
V
V
the CE line is high, and
the OE line is low.
CC
PP
Verify
is at the proper V
Inhibit
Identity Mode
is at the proper level,
Input
V
A0
V
IH
IL
0
1
0
7
2004 Microchip Technology Inc.
H
O
0
0
6
level,
O
1
0
5
O
0
0
4
Output
O
1
1
3
O
0
1
2
O
0
0
1
1
0
O
0
29
8C
H
e
x
IL
H
.