– Single Cycle Reprogram (Erase and Program)
– Internal Address and Data Latches for 64 Bytes
• Internal Program Control and Timer
• Hardware and Software Data Protection
• Fast Program Cycle Times
– Page(64Byte)ProgramTime–10ms
– Chip Erase Time– 10 ms
• DATA Polling for End of Program Detection
• Low-power Dissipation
– 50mAActiveCurrent
–300 µA CMOS Standby Current
• Typical Endurance > 10,000 Cycles
• Single 5V ± 10% Supply
• CMOS and TTL Compatible Inputs and Outputs
• Commercial and Industrial Temperature Ranges
Description
The AT29C256 is a five-volt-only in-system Flash programmable and erasable read
only memory (PEROM). Its 256K of memory is organized as 32,768 words by 8 bits.
Manufactured with Atmel’s advanced nonvolatile CMOS technology, the device offers
access times to 70 ns with power dissipation of just 275 mW. When the device is
deselected, the CMOS standby current is less than 300 µA. The device endurance is
such that any sector can typically be written to in excess of 10,000 times.
256K (32K x 8)
5-volt Only
Flash Memory
AT29C256
Pin Configurations
Pin NameFunction
A0 - A14Addresses
CE
OE
WE
I/O0 - I/O7Data Inputs/Outputs
NCNo Connect
DCDon’t Connect
PLCC and LCC Top View
Note:PLCC package pins 1 and 17 are
DON’T CONNECT.
Chip Enable
Output Enable
Write Enable
A7
432
5
A6
6
A5
7
A4
8
A3
9
A2
10
A1
11
A0
12
NC
13
I/O0
14151617181920
I/O1
A12WEDC
I/O2
GND
1
DC
VCC
A14
323130
I/O3
I/O4
A13
29
28
27
26
25
24
23
22
21
I/O5
A8
A9
A11
NC
OE
A10
CE
I/O7
I/O6
DIP Top View
WE
A12
I/O0
I/O1
I/O2
GND
TSOP Top View
22
OE
23
A11
24
A9
25
A8
26
A13
27
A14
28
VCC
1
WE
2
A12
3
A7
4
A6
5
A5
6
A4
7
A3
A7
A6
A5
A4
A3
A2
A1
A0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Type 1
28
VCC
27
A14
26
A13
25
A8
24
A9
23
A11
22
OE
21
A10
20
CE
19
I/O7
18
I/O6
17
I/O5
16
I/O4
15
I/O3
21
A10
20
CE
19
I/O7
18
I/O6
17
I/O5
16
I/O4
15
I/O3
14
GND
13
I/O2
12
I/O1
11
I/O0
10
A0
9
A1
8
A2
Rev. 0046O–FLASH–06/02
1
Page 2
Block Diagram
To allow for simple in-system reprogrammability, the AT29C256 does not require high
input voltages for programming. Five-volt-only commands determine the operation of
the device. Reading data out of the device is similar to reading from a static RAM.
Reprogramming the AT29C256 is performed on a page basis; 64 bytes of data are
loaded into the device and then simultaneously programmed. The contents of the entire
device may be erased by using a six-byte software code (although erasure before programming is not needed).
During a reprogram cycle, the address locations and 64 bytes of data are internally
latched, freeing the address and data bus for other operations. Following the initiation of
a program cycle, the device will automatically erase the page and then program the
latched data using an internal control timer. The end of a program cycle can be detected
by DATA
access for a read, program or chip erase can begin.
polling of I/O7. Once the end of a program cycle has been detected a new
Device Operation
READ: The AT29C256 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 whenever
CE
or OE is high. This dual-line control gives designers flexibility in preventing bus
contention.
BYTE LOAD: A byte load is performed by applying a low pulse on the WE
with CE
edge of CE
CE
software codes for data protection and chip erasure.
or WE low (respectively) and OE high. The address is latched on the falling
or WE, whichever occurs last. The data is latched by the first rising edge of
or WE. Byte loads are used to enter the 64 bytes of a page to be programmed or the
page is to be changed, data for the entire page must be loaded into the device. Any byte
that is not loaded during the programming of its page will be indeterminate. Once the
bytes of a page are loaded into the device, they are simultaneously programmed during
the internal programming period. After the first data byte has been loaded into the
device, successive bytes are entered in the same manner. Each new byte to be programmed must have its high-to-low transition on WE
high transition of WE
(or CE) of the preceding byte. If a high-to-low transition is not
detected within 150 µs of the last low-to-high transition, the load period will end and the
internal programming period will start. A6 to A14 specify the page address. The page
address must be valid during each high-to-low transition of WE
the byte address within the page. The bytes may be loaded in any order; sequential
loading is not required. Once a programming operation has been initiated, and for the
duration of t
, a read operation will effectively be a polling operation.
WC
SOFTWARE DATA PROTECTION: A software controlled data protection feature is
available on the AT29C256. Once the software protection is enabled a software algorithm must be issued to the device before a program may be performed. The software
protection feature may be enabled or disabled by the user; when shipped from Atmel,
the software data protection feature is disabled. To enable the software data protection,
a series of three program commands to specific addresses with specific data must be
performed. After the software data protection is enabled the same three program commands must begin each program cycle in order for the programs to occur. All software
program commands must obey the page program timing specifications. Once set, the
software data protection feature remains active unless its disable command is issued.
Power transitions will not reset the software data protection feature, however the software feature will guard against inadvertent program cycles during power transitions.
(or CE) within 150 µs of the low-to-
(or CE). A0 to A5 specify
Once set, software data protection will remain active unless the disable command
sequence is issued.
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
, a read operation will effectively be a polling operation.
WC
After the software data protection’s three-byte command code is given, a byte load is
performed by applying a low pulse on the WE
tively) and OE
high. The address is latched on the falling edge of CE or WE, whichever
occurs last. The data is latched by the first rising edge of CE
or CE input with CE or WE low (respec-
or WE. The 64 bytes of
data must be loaded into each sector by the same procedure as outlined in the program
section under device operation.
HARDWARE DATA PROTECTION: Hardware features protect against inadvertent
programs to the AT29C256 in the following ways: (a) V
(typical), the program function is inhibited; (b) V
reached the V
sense level, the device will automatically time out 5 ms (typical) before
CC
CC
programming; (c) Program inhibit – holding any one of OE
sense – if VCCis below 3.8V
CC
power on delay – once VCChas
low, CE high or WE high
inhibits program cycles; and (d) Noise filter – pulses of less than 15 ns (typical) on the
WE
or CE inputs will not initiate a program cycle.
0046O–FLASH–06/02
3
Page 4
PRODUCT IDENTIFICATION: The product identification mode identifies the device
and manufacturer and may be accessed by a hardware operation. For details, see
Operating Modes or Product Identification.
DATA POLLING:The AT29C256 features DATA
gram cycle. During a program cycle an attempted read of the last byte loaded will result
in the complement of the loaded data on I/O7. Once the program cycle has been completed, true data is valid on all outputs and the next cycle may begin. DATA
begin at any time during the program cycle.
TOGGLE BIT: In addition to DATA
determining the end of a program or erase cycle. During a program or erase operation,
successive attempts to read data from the device will result in I/O6 toggling between
one and zero. Once the program cycle has completed, I/O6 will stop toggling and valid
data will be read. Examining the toggle bit may begin at any time during a program
cycle.
OPTIONAL CHIP ERASE MODE: The entire device can be erased by using a six-byte
software code. Please see Software Chip Erase application note for details.
Absolute Maximum Ratings*
Temperature Under Bias................................ -55°Cto+125°C
Storage Temperature ..................................... -65°Cto+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
polling to indicate the end of a pro-
polling may
polling the AT29C256 provides another method for
*NOTICE:Stresses beyond those listed under “Absolute
Maximum Ratings” may cause permanent damage to the device. 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.
Voltage on OE
with Respect to Ground ...................................-0.6V to +13.5V
4
AT29C256
0046O–FLASH–06/02
Page 5
DC and AC Operating Range
AT29C256
AT29C256-70AT29C256-90AT29C256-12AT29C256-15
Operating
Temperature (Case)
V
Power Supply5V ± 5%5V± 10%5V± 10%5V± 10%
CC
Note:
Not recommended for New Designs.
Com.0°C-70°C0°C-70°C0°C-70°C
Ind.-40°C-85°C-40°C-85°C-40°C-85°C
Operating Modes
ModeCEOEWEAiI/O
ReadV
Program
(2)
5V Chip EraseV
Standby/Write InhibitV
IL
V
IL
IL
IH
Write InhibitXXV
Write InhibitXV
Output DisableXV
High Voltage Chip EraseV
IL
Product Identification
V
Hardware
Software
(5)
IL
Notes: 1. X can be VILor VIH.
2. Refer to AC Programming Waveforms.
3. V
= 12.0V ± 0.5V.
H
4. Manufacturer Code: 1F, Device Code: DC.
5. See details under Software Product Identification Entry/Exit.
V
IL
V
IH
V
IH
(1)
X
IL
IH
(3)
V
H
V
IL
V
IH
V
IL
V
IL
AiD
AiD
Ai
OUT
IN
XXHighZ
IH
X
XHighZ
V
IL
V
IH
A1-A14 = VIL,A9=VH,A0=VILManufacturer Code
XHighZ
A1-A14 = VIL,A9=VH,A0=VIHDevice Code
A0 = V
A0 = V
IL
IH
Manufacturer Code
Device Code
0°C-70°C
-40°C-85°C
(4)
(4)
(4)
(4)
DC Characteristics
SymbolParameterConditionMinMaxUnits
I
LI
I
LO
I
SB1
I
SB2
I
CC
V
IL
V
IH
V
OL
V
OH1
V
OH2
0046O–FLASH–06/02
Input Load CurrentVIN=0VtoV
Output Leakage CurrentV
=0VtoV
I/O
CC
CC
VCCStandby Current CMOSCE =VCC-0.3VtoV
VCCStandby Current TTLCE =2.0VtoV
VCCActive Currentf = 5 MHz; I
CC
= 0 mA50mA
OUT
CC
10µA
10µA
300µA
3mA
Input Low Voltage0.8V
Input High Voltage2.0V
Output Low VoltageIOL=2.1mA0.45V
Output High VoltageIOH=-400µA2.4V
Output High Voltage CMOSIOH=-100µA;VCC=4.5V4.2V
5
Page 6
AC Read Characteristics
SymbolParameter
t
ACC
t
CE
t
OE
t
DF
t
OH
Note:
(1)
(2)
(3)(4)
Address to Output Delay7090120150ns
CE to Output Delay7090120150ns
OE to Output Delay040040050070ns
CE or OE to Output Float025025030040ns
Output Hold from OE,CEor Address,
whichever occurred first
Not recommended for New Designs.
AC Read Waveforms
(1)(2)(3)(4)
AT29C256-70AT29C256-90AT29C256-12
AT29C256-15
MinMax
0000ns
UnitsMinMaxMinMaxMinMax
Notes: 1. CE may be delayed up to t
2. OE
may be delayed up to tCE-tOEafter the falling edge of CE without impact on tCEor by t
without impact on t
3. t
is specified from OE or CE whichever occurs first (CL = 5 pF).
DF
ACC
.
4. This parameter is characterized and is not 100% tested.
6
AT29C256
ACC-tCE
after the address transition without impact on t
ACC
.
ACC-tOE
after an address change
0046O–FLASH–06/02
Page 7
Input Test Waveforms and Measurement Level
tR,tF<5ns
Output Test Load
Pin Capacitance
f=1MHz,T=25°C
(1)
AT29C256
SymbolTypMaxUnitsConditions
C
IN
C
OUT
Note:1. This parameter is characterized and is not 100% tested.
46pFV
812pFV
IN
OUT
=0V
=0V
0046O–FLASH–06/02
7
Page 8
AC Byte Load Characteristics
SymbolParameterMinMaxUnits
t
AS,tOES
t
AH
t
CS
t
CH
t
WP
t
DS
t
DH,tOEH
t
WPH
Address, OE Set-up Time0ns
Address Hold Time50ns
Chip Select Set-up Time0ns
Chip Select Hold Time0ns
Write Pulse Width (WE or CE)90ns
Data Set-up Time35ns
Data, OE Hold Time0ns
Write Pulse Width High100ns
AC Byte Load Waveforms
WE Controlled
Controlled
CE
8
AT29C256
0046O–FLASH–06/02
Page 9
AT29C256
Program Cycle Characteristics
SymbolParameterMinMaxUnits
t
WC
t
AS
t
AH
t
DS
t
DH
t
WP
t
BLC
t
WPH
WriteCycleTime10ms
Address Set-up Time0ns
Address Hold Time50ns
Data Set-up Time35ns
Data Hold Time0ns
Write Pulse Width90ns
Byte Load Cycle Time150µs
Write Pulse Width High100ns
Program Cycle Waveforms
(1)(2)(3)
Notes: 1. A6 through A14 must specify the page address during each high-to-low transition of WE (or CE).
2. OE
must be high when WE and CE are both low.
3. All bytes that are not loaded within the page being programmed will be indeterminate.
0046O–FLASH–06/02
9
Page 10
Software Data Protection
Enable Algorithm
(1)
Software Data Protection
Disable Algorithm
(1)
LOAD DATA AA
TO
ADDRESS 5555
LOAD DATA 55
TO
ADDRESS 2AAA
LOAD DATA A0
TO
ADDRESS 5555
LOAD DATA
TO
PAGE (64 BYTES)
WRITES ENABLED
ENTER DATA
(4)
PROTECT STATE
Notes: 1. Data Format: I/O7 - I/O0 (Hex);
Address Format: A14 - A0 (Hex).
2. Data Protect state will be re-activated at end of program cycle.
3. Data Protect state will be deactivated at end of program period.
4. 64 bytes of data MUST BE loaded.
LOAD DATA AA
TO
ADDRESS 5555
LOAD DATA 55
TO
ADDRESS 2AAA
LOAD DATA 80
(2)
TO
ADDRESS 5555
LOAD DATA AA
TO
ADDRESS 5555
LOAD DATA 55
TO
ADDRESS 2AAA
LOAD DATA 20
TO
ADDRESS 5555
EXIT DATA
PROTECT STATE
(3)
LOAD DATA
Software Protected Program Cycle Waveform
TO
PAGE (64 BYTES)
(1)(2)(3)
(4)
Notes: 1. A6 through A14 must specify the page address during each high-to-low transition of WE (or CE) after the software code has
been entered.
2. OE
must be high when WE and CE arebothlow.
3. All bytes that are not loaded within the page being programmed will be indeterminate.
10
AT29C256
0046O–FLASH–06/02
Page 11
AT29C256
Data Polling Characteristics
(1)
SymbolParameterMinTypMaxUnits
t
DH
t
OEH
t
OE
t
WR
Data Hold Time0ns
OE Hold Time10ns
OE to Output Delay
(2)
Write Recovery Time0ns
Notes: 1. These parameters are characterized and not 100% tested.
2. See t
spec in AC Read Characteristics.
OE
Data Polling Waveforms
ns
Toggle Bit Characteristics
(1)
SymbolParameterMinTypMaxUnits
t
DH
t
OEH
t
OE
t
OEHP
t
WR
Data Hold Time0ns
OE Hold Time10ns
OE to Output Delay
(2)
OE High Pulse150ns
Write Recovery Time0ns
Notes: 1. These parameters are characterized and not 100% tested.
2. See t
Toggle Bit Waveforms
spec in AC Read Characteristics.
OE
(1)(2)(3)
ns
Notes: 1. Toggling either OE or CE or both OE and CE will operate toggle bit.
2. Beginning and ending state of I/O6 will vary.
3. Any address location may be used but the address should not vary.
0046O–FLASH–06/02
11
Page 12
Software Product Identification Entry
(1)
Software Product Identification Exit
(1)
LOAD DATA AA
TO
ADDRESS 5555
LOAD DATA 55
TO
ADDRESS 2AAA
LOAD DATA 90
TO
ADDRESS 5555
PAUSE 10 mSENTER PRODUCT
IDENTIFICATION
MODE
Notes: 1. Data Format: I/O7 - I/O0 (Hex);
Address Format: A14 - A0 (Hex).
2. A1 - A14 = V
.
IL
Manufacturer Code is read for A0 = V
Device Code is read for A0 = V
3. The device does not remain in identification mode if
powered down.
4. The device returns to standard operation mode.
5. Manufacturer Code is 1F. The Device Code is DC.
28T28-lead, Plastic Thin Small Outline Package (TSOP)
Not recommended for New Designs.
Package Type
14
AT29C256
0046O–FLASH–06/02
Page 15
Packaging Information
32J – PLCC
AT29C256
1.14(0.045) X 45˚
B
e
0.51(0.020)MAX
45˚ MAX (3X)
Notes:1. This package conforms to JEDEC reference MS-016, Variation AE.
2. Dimensions D1 and E1 do not include mold protrusion.
Allowable protrusion is .010"(0.254 mm) per side. Dimension D1
and E1 include mold mismatch and are measured at the extreme
material condition at the upper or lower parting line.
Atmel Corporation makes no warranty for the use of its products, other than those expressly contained in the Company’s standard warranty
which is detailed in Atmel’s Terms and Conditions located on the Company’s web site. The Company assumes no responsibility for any errors
which may appear in this document, reserves the right to change devices or specifications detailed herein at any time without notice, and does
not make any commitment to update the information contained herein. No licenses to patents or other intellectual property of Atmel are granted
by the Company in connection with the sale of Atmel products, expressly or by implication. Atmel’s products are not authorized for use as critical
components in life support devices or systems.
AT ME L®is the registered trademark of Atmel.
Other terms and product names may be the trademarks of others.
Printed on recycledpaper.
0046O–FLASH–06/02xM
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