ATMEL AT28HC256F-12JI, AT28HC256F-12JC, AT28HC256F-12FM-883, AT28HC256F-12DM-883, AT28HC256E-90UM-883 Datasheet
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AT28HC256
256 (32K x 8)
High Speed
CMOS
E2PROM
Features
•
Fast Read Access Time - 70 ns
•
Automatic Page Write Operation
Internal Address and Data Latches for 64-Bytes
Internal Control Timer
•
Fast Write Cycle Times
Page Write Cycle Tim e: 3 ms or 1 0 ms Maxim um
1 to 64-Byte Page Write Operation
•
Low Power Dissipation
80 mA Active Current
3 mA Standby Current
•
Hardware and Software Data Protection
•
DATA Polling for End of Write Detection
•
High Reliabili ty C MOS Technology
Endurance: 104 or 105 Cycles
Data Retention: 10 Years
•
Single 5V ± 10% Supply
•
CMOS and TTL Compatible Inputs and Outputs
•
JEDEC Approved Byte-Wide Pinout
•
Full Military, Commercial, and Industrial Temperature Ranges
Description
The AT28HC256 is a high-performance Electrically Erasable and Programmable
Read Only Memory. Its 256K of memory is organized as 32,768 words by 8 bits.
Manufactured with Atmel’s advanced nonvolatile CMOS technology, the AT28HC256
offers access times to 70 ns with power dissipation of ju st 440 mW. When the
AT28HC256 is deselected, the standby current is less than 5 mA.
(continued)
Note: PLCC package pins 1 and
17 are DON’T CONNECT.
CERDIP, PDIP,
FLATPACK
Top View
LCC, PLCC
Top View
Pin Name Function
A0 - A14 Addresses
CE Chip Enable
OE Output E nable
WE Write Enable
I/O0 - I/O7 Data Inputs/Outputs
NC No Connect
DC Don’t Connect
Pin Configurations
TSOP
Top View
PGA
Top View
0007F
AT28HC256
2-279
Block Diagram
The AT28HC25 6 is accessed like a Static RAM for the
read or write cycle without the need for external components. The device contains a 64-byte page register to allow writin g of up to 64-bytes simultaneously. During a
write cycle, the address and 1 to 64-bytes of data are internally latched, freeing the addresses and data bus for
other operations. Following the initiation of a write cycle,
the device will automatically write the latched data using
an internal control timer. The end of a write cycle can be
detected by
DATA polling of I/O7. Once the end of a write
cycle has been detected a new access for a read or write
can begin.
Atmel’s 28HC256 has additional features to ensure high
quality and manufacturability. The device utilizes internal
error correc tion for extended endurance and improved
data retention characteristics. An optional software data
protection mechanism is available to guard against inadvertent writes. The device also includes an extra 64-bytes
of E
2
PROM for device identification or tracking.
Description (Continued)
Temperature Under Bias.................-55°C to +125°C
Storage Temperature...................... -65°C to +150°C
All Input Voltages
(including NC Pins)
with Respect to Ground ................... -0.6V to +6.25V
All Output Voltages
with Respect to Ground .............-0.6V to V
CC
+ 0.6V
Voltage on OE and A9
with Respect to Ground ................... -0.6V to +13.5V
*NOTICE: Stresses beyond those listed unde r “Abso lute Maxi-
mum Ratings” may cause permanent da ma ge to th e devi ce .
This is a stress rating only and functional operation of the
device at these or any other conditions beyond those indicated in the operational sections of this specification is not
implied. Exposure to absolute maximum rating conditions
for extended periods may affect device reliability.
Absolute Maximum Ratings*
2-280 AT28HC256
Device Operation
READ: The AT28HC256 is accessed like a Static RAM.
When
CE and OE are low and WE is high, the data stored
at the memory location determined by the address pins is
asserted on the outputs. The outputs are put in the high
impedance state when either
CE or OE is high. This dualline control gives designers flexibility in preventing bus
contention in their system.
BYTE WRITE: A low pulse on the
WE or CE input with CE
or
WE low (respectively) and OE high initiates a write cy-
cle. The address is latched on the falling edge of
CE or
WE, whichever occurs last. The data is latched by the firs t
rising edge of
CE or WE. Once a byte write has been
started it will automatically time itself to completion. Once
a programming operation has been initiated and for the
duration of t
WC
, a read operation will effectively be a poll-
ing operation.
PAGE WRITE: The page write operation of the
AT28HC256 allows 1 to 64-bytes of data to be wr itten into
the device during a single internal programming period. A
page write operation is initiated in the same manner as a
byte write; the first byte written can then be followed by 1
to 63 additional bytes. Each successive byte must be written within 150 µs (t
BLC
) of the previous byte. If the t
BLC
limit is exceeded the AT28C256 will cease accepting data
and commence the inte rnal programming operation. All
bytes during a page write operation must reside on the
same page as defined by the state of the A6 - A14 inputs.
That is, for each
WE high to low transition during the page
write operation, A6 - A14 must be the same.
The A0 to A5 inputs are used to specify which bytes within
the page are to be written. The bytes may be loaded in any
order and may be altered within the same load period.
Only bytes which are specified for writing will be written;
unnecessary cycling of other bytes within the page does
not occur.
DATA POLLING: The AT28HC256 features DATA Polling
to indicate the end of a write cycle. During a byte or page
write cycle an attempted read of the last byte written will
result in the complem ent of the written data to be presented on I/O7. Once the write cycle has been completed,
true data is valid on all outputs, and the next write cycle
may begin.
DATA Polling may begin at anytime during the
write cycle.
TOGGLE BIT: In addition to
DATA Polling the
AT28HC256 provides another method for determining the
end of a write cycle. During the write operation, successive attempts to read data from the device will result in
I/O6 toggling between one and zero. Once the write has
completed, I/O6 will stop toggling and valid data will be
read. Testing the toggle bit may begin at any time during
the write cycle.
(continued)
DATA PROTECTION: If precautions are not taken, inadvertent writes to any 5-volt-only nonvolatile memory may
occur during transition of the host system power supply.
Atmel has incorporated both hardware and software features that will protect the memory against inadvertent
writes.
HARDWARE PROTECTION: Hardware features protect
against inadvertent writes to the AT28HC256 in the following ways: (a) V
CC
sense - if VCC is below 3.8V (typical) the
write function is inhibited; (b) V
CC
power-on delay - once
V
CC
has reached 3.8V the device will automatically time
out 5 ms typical) before allowing a write: (c) write inhibit holding any one of
OE low, CE high or WE high inhibits
write cycles; (d) noise filter - pulses of less than 15 ns (typical) on the
WE or CE inputs will not initiate a write cycle.
SOFTWARE DATA PROTECTION: A software controlled
data protection feature has been implemented on the
AT28HC256. When enabled, the software data protection
(SDP), will prevent inadvertent writes. The SDP feature
may be enabled or disabled by the user; the AT28HC256
is shipped from Atmel with SDP disabled.
SDP is enabled by the h ost system issuing a series of
three write co mmands; three specific bytes of data are
written to three specific addresses (refer to Software Data
Protection Algorithm). After writing the 3-byte command
sequence and after t
WC
the entire AT28HC256 will be protected against inadvertent write operations. It should be
noted, that once protected the host may still perform a
byte or page write to the AT28HC256. This is done by preceding the data to be written by the same 3-byte command
sequence.
Once set, SDP will remain active unless the disable command sequence is issued. Power transitions do not disable SDP and SDP will protect the AT28HC256 during
power-up and power-down conditions. All command sequences must conform to the page write timing specifications. It should also be noted that the data in the enable
and disable command sequences is not written to the device and the memory addresses used in the sequence
may be written with data in either a byte or page write operation.
After setting SDP, any attempt to write to the device without the three byte command sequence will start the internal write timers. No data will be written to the device; however, for the duration of t
WC
, read operations will effec-
tively be polling operations.
AT28HC256
2-281
Symbol Parameter Condition Min Max Units
I
LI
Input Load Current VIN = 0V to VCC + 1V 10 µA
I
LO
Output Leakage Current V
I/O
= 0V to V
CC
10 µA
I
SB1
VCC Standby Current TTL CE = 2.0V to VCC + 1V
AT28HC256-90, -12 3 mA
AT28HC256-70 60 mA
I
SB2
VCC Standby Current CMOS CE = -3.0V to VCC + 1V AT28HC256-90, -12 300 µA
I
CC
V
CC
Active Current f = 5 MHz; I
OUT
= 0 mA 80 mA
V
IL
Input Low Voltage 0.8 V
V
IH
Input High Voltage 2.0 V
V
OL
Output Low Voltage IOL = 6.0 mA .45 V
V
OH
Output High Voltage I
OH
= -4 mA 2.4 V
DC Characteristics
AT28HC256-70 AT28HC256-90 AT28HC256-12
Operating
Temperature (Case)
Com. 0°C - 70°C 0°C - 70°C 0°C - 70°C
Ind. -40°C - 85°C -40°C - 85°C -40°C - 85°C
Mil. -55°C - 125°C -55°C - 125°C
V
CC
Power Supply 5V ± 10% 5V ± 10% 5V ± 10%
DC and AC Operating Range
Mode CE OE WE I/O
Read V
IL
V
IL
V
IH
D
OUT
Write
(2)
V
IL
V
IH
V
IL
D
IN
Standby/Write Inhibit V
IH
X
(1)
X High Z
Write Inhibit X X V
IH
Write Inhibit X V
IL
X
Output Disable X V
IH
X High Z
Chip Erase V
IL
VH
(3)
VIL High Z
3. VH = 12.0V ± 0.5V.
Notes: 1. X can be V
IL
or VIH.
2. Refer to AC Programming Waveforms.
Operating Modes
DEVICE IDENTIFICATION : An extra 64-bytes of
E
2
PROM memory are available to the user for device
identification. By raising A9 to 12V ± 0.5V and using address locations 7FC0H to 7FFFH the additional bytes may
be written to or read from in the same manner as the regular memory array.
OPTIONAL CHIP ERASE MODE: The entire device can
be erased using a 6-byte software code. Please see Software Chip Erase application note for details.
Device Operation (Continued)
2-282 AT28HC256
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