UVEPROM
Austin Semiconductor, Inc.
256K UVEPROM
UV Erasable Programmable
Read-Only Memory
AVAILABLE AS MILITARY
SPECIFICATIONS
• -55C to 125C operation
• MILITARY Processing Method MIL-PRF-38535, Class Q
• Commercial Version Available
AS27C256
PIN ASSIGNMENT
(Top View)
28-Pin DIP (J)
(600 MIL)
V
PP
A12
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
Vcc
A14
A13
A8
A9
A11
G\
A10
E\
DQ7
DQ6
DQ5
DQ4
DQ3
FEATURES
Organized 32,768 x 8
Single +5V ±10% power supply
Pin-compatible with existing 256K ROM’s and EPROM’s
All inputs/outputs fully TTL compatible
Power-saving CMOS technology
Very high-speed FLASHRITE Pulse Programming
3-state output buffers
400-mV DC assured noise immunity with standard TTL
loads
• Latchup immunity of 250 mA on all input and output pins
• Low power dissipation (CMOS Input Levels)
-Active - 165mW Worst Case
-Standby - 1.7mW Worst Case (CMOS-input levels)
* FUTURE High Speed Offerings: 55ns, 70ns, 90ns
•
•
•
•
•
•
•
•
32-Pin LCC (ECA)
(450 x 550 mils)
A7
A12
A12
A14
6
A10
V
PP
NC
NC
V
CC
V
CC
A15
A14
CE2
A13
4 3 2 1 32 31 30
OPTIONS
• Timing
120ns access
150ns access
170ns access
200ns access
250ns access
300ns access
55ns access
70ns access
90ns access
MARKING
-12
-15
-17
-20
-25
-30
-55
-70
-90
A6
5
A7
A5
6
A6
A4
7
A5
A3
8
A4
A2
9
A3
A2 10
A1
A1 11
A0
A0 12
NC
DQ1 13
DQ0
29
A8
\
WE
28
A9
A13
27
A11
A8
26
NC
A9
25
G\
A11
24
A10
\
OE
23
E\
A10
22
DQ7
\
CE1
21
DQ6
DQ8
14 15 16 17 18 19 20
Pin Name
Pin
A14
A0 -
Name
DQ0-DQ7
E\
G\
GND
V
CC
Address
Inputs (programming)/Outputs
Chip Enable/Power Down
Output Enable
Ground
5V Supply
13V Programming Power Supply
• Package(s)
Ceramic DIP (600mils) J
No. 110
Ceramic LCC (450 x 550 mils) ECA No. 208
• Processing / Operating Temperature Ranges
Full Military (-55
o
C to +125
o
C)
M
Industrial (-40°C to +85°C)
I
o
o
Military Temp (-55 C to +125 C) XT
V
PP
For more products and information
please visit our web site at
www.austinsemiconductor.com
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
AS27C256
Rev. 2.0 7/06
1
DQ1
DQ2
DQ2
DQ3
V
SS
GND
DQ4
NC
DQ5
DQ3
DQ6
DQ4
DQ7
DQ5
Function
Function
Inputs
UVEPROM
Austin Semiconductor, Inc.
GENERAL DESCRIPTION
The AS27C256 series is a set of 262,144 bit, ultraviolet-light
erasable, electrically programmable read-only
memories.
These devices are fabricated using power-saving CMOS tech-
nology for high speed and simple interface with MOS and bipo-
lar circuits. All inputs (including program data inputs) can be
driven by Series 54 TTL circuits without the use of external
pullup resistors. Each output can drive one Series 54 TTL
circuit without external resistors. The data outputs are 3-state
for connecting multiple devices to a
common bus. The
AS27C256 is pin-compatible with 28-pin 256K ROMs and
EPROMs. It is offered in a 600mil dual-in-line ceramic package
(J suffix) and a 450 x 550 mil ceramic LCC (ECA suffix) rated for
operation from -55°C to 125°C.
Because this EPROM operates from a single 5V supply (in
the read mode), it is ideal for use in microprocessor-based sys-
tems. One other supply (12.75V) is needed for programming.
All programming signals are TTL level. This device is
pro-
grammable by the AMD FLASHRITE Pulse programming algo-
rithm. The FLASHRITE Pulse programming algorithm uses a
V
PP
of 12.75VV and a V
CC
of 6.25V for a nominal programming
time of four seconds. For programming outside the system,
existing EPROM programmers can be used. Locations can be
programmed singly, in blocks, or at random.
AS27C256
FUNCTIONAL BLOCK DIAGRAM*
EPROM 32,768 x 8
A0
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
A11
A12
A13
A14
E\
G\
10
9
8
7
6
5
4
3
25
24
21
23
2
26
27
20
22
0
A
0
32,767
A
A
A
A
A
A
A
A
11
12
13
15
16
17
18
19
DQ0
DQ1
DQ2
DQ3
DQ4
DQ5
DQ6
DQ7
14
[PWR DWN]
&
EN
* This symbol is in accordance with ANSI/IEEE std 91-1984 and IEC Publication 617-12.
AS27C256
Rev. 2.0 7/06
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
2
UVEPROM
Austin Semiconductor, Inc.
OPERATION
The seven modes of operation for the AS27C256 are listed in Table 1. The read mode requires a single 5V supply.
All inputs are TTL level except for V
PP
during programming (12.75V for FLASHRITE Pulse), and (12V) on A9
for signature mode.
AS27C256
TABLE 1. OPERATION MODES
FUNCTION
(PINS)
E\
G\
V
PP
V
CC
A9
A0
DQ0-DQ7
READ
V
IL
V
IL
X
1
V
CC
X
X
Data Out
OUTPUT
STANDBY PROGRAMMING
DISABLE
V
IL
V
IH
X
1
V
CC
X
X
High-Z
V
IH
X
X
1
V
CC
+/-.3V
X
X
High-Z
V
IL
V
IH
V
PP
V
CC
X
X
Data In
MODE*
VERIFY
V
IH
V
IL
V
PP
V
CC
X
X
Data Out
PROGRAM
SIGNATURE MODE
INHIBIT
V
IL
V
IH
X
V
PP
V
CC
X
X
High-Z
V
ID
2
V
IL
V
CC
V
CC
V
ID
2
V
IH
CODE**
MFG
DEVICE
01h
10h
V
IL
1
2
For normal standby & read operation, VPP is Don't Care X.
V
ID
= 12V +/- .5V
NOTES:
* X can be V
IL
or V
IH
**
Die is AMD. User can program on benchtop programmer by selecting AM27C256 from the device
type selection menu.
AS27C256
Rev. 2.0 7/06
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
3
UVEPROM
Austin Semiconductor, Inc.
READ/OUTPUT DISABLE
When the outputs of two or more AS27C256 are connected in
parallel on the same bus, the output of any particular device in
the circuit can be read with no interference from the compet-
ing outputs of the other devices. To read the output of the
selected AS27C256, a low-level signal is applied to E\ and G\.
All other devices in the circuit should have their outputs
disabled by applying a high-level signal to one of these pins.
Output data is accessed at pins DQ0 through DQ7.
AS27C256
FLASHRITE PULSE PROGRAMMING
The AS27C256 EPROM is programmed by using the AMD
FLASHRITE Pulse programming algorithm as illustrated by the
flowchart in Figure 1. This algorithm programs the device in a
nominal time of 4 seconds. Actual programming time varies as
a function of the programmer used.
Data is presented in parallel (eight bits) on pins DQ0 to DQ7.
Once addresses and data are stable, E\ is pulsed.
The FLASHRITE Pulse programming algorithm uses initial
pulses of 100 microseconds (µs) followed by a byte-verifica-
tion step to determine when the addressed byte has been suc-
cessfully programmed. Up to 25 100µs pulses per byte are
provided before a failure is recognized.
The programming mode is achieved when V
PP
= 12.75V,
V
CC
= 6.25V, G\ = V
IH
, and E\ = V
IL
. More than one device can be
programmed when the devices are connected in parallel. Loca-
tions can be programmed in any order. When the AMD
FLASHRITE Pulse programming routine is completed, all bits
are verified with V
CC
= V
PP
= 5V.
LATCHUP IMMUNITY
Latchup immunity on the AS27C256 is a minimum of 250mA on
all inputs and outputs. This feature provides latchup
im-
munity beyond any potential transients at the printed
cir-
cuit board level when the EPROM is interfaced to industry
standard TTL or MOS logic devices. Input/output layout
approach controls latchup without compromising performance
or packing density.
POWER DOWN
Active I
CC
supply current can be reduced from 25mA (AS27C256-
12 through AS27C256-25) to 1mA (TTL-level inputs) or 300µA
(CMOS-level inputs) by applying a high TTL/CMOS signal to
the E\ pin. In this mode all outputs are in the high-impedance
state.
PROGRAM INHIBIT
Programming can be inhibited by maintaining a high-level
input on E\.
ERASURE
Before programming, the AS27C256 is erased by exposing the
chip through the transparent lid to a high-intensity ultraviolet
light (wavelength 2537 Å). EPROM erasure before program-
ming is necessary to ensure that all bits are in the logic-high
state. Logic-lows are programmed into the desired locations. A
programmed logic-low can be erased only by ultraviolet light.
The recommended minimum exposure dose (UV intensity x ex-
posure time) is 15W•s/cm
2
. A typical 12mW/cm
2
, filterless UV
lamp erases the device in 21 minutes. The lamp should be
located about 2.5cm above the chip during erasure. After era-
sure, all bits are in the high state. It should be noted that normal
ambient light contains the correct wavelength for erasure; there-
fore, when using the AS27C256, the window should be covered
with an opaque label.
PROGRAM VERIFY
Programmed bits can be verified with V
PP
= 12.75V when G\ =
V
IL
, and E\ = V
IH
.
SIGNATURE MODE
The signature mode provides access to a binary code
iden-
tifying the manufacturer and device type. This mode is acti-
vated when A9 is forced to 12V ±0.5V. Two identifier bytes are
accessed by A0 (terminal 10); i.e., A0=V
IL
accesses the manu-
facturer code, which is output on DQ0-DQ7; A0=V
IH
accesses
the device code, which is also output on DQ0-DQ7. All other
addresses must be held at VIL. Each byte contains odd parity
on bit DQ7. The manufacturer code for these devices is 01h
and the device code is 10h.
AS27C256
Rev. 2.0 7/06
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
4
UVEPROM
Austin Semiconductor, Inc.
AS27C256
FIGURE 1. FLASHRITE PULSE PROGRAMMING FLOWCHART
Start
Address = First Location
VCC=6.25V, VPP=12.75V
X=0
Program One 100us Pulse
Increment X
Programming
Section
X = 25 ?
NO
Program
Verify
Byte?
Pass
Last
Address?
YES
FAIL
Increment Address
NO
Yes
VCC = VPP = 5.25V
Read
Verify
Section
READ
Verify
Bytes?
FAIL
Device Failed
Pass
Device Passed
AS27C256
Rev. 2.0 7/06
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
5
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