Features
•
Fast Read Access Time – 70 ns
•
5-volt Only Reprogramming
•
Sector Program Operation
– Single Cycle Reprogram (Erase and Program)
– 1024 Sectors (256 Bytes/Sector)
– Internal Address and Data Latches for 256 Bytes
Internal Program Control and Timer
Hardware and Software Data Protection
Two 8K Bytes Boot Blocks with Lockout
Fast Sector Program Cycle Time – 10 ms
DATA Polling for End of Program Detection
Low Power Dissipation
– 40 mA Active Current
– 100 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
•
•
•
•
•
•
•
•
•
•
2-megabit
(256K x 8)
5-volt Only
Flash Memory
AT29C020
Description
The AT29C020 is a 5-volt-only in-system Flash programmable and erasable read-only
memory (PEROM). Its 2 megabits of memory is organized as 262,144 bytes. Manu-
factured with Atmel’s advanced nonvolatile CMOS technology, the device offers
access times to 70 ns with power dissipation of just 220 mW over the commercial tem-
perature range. When the device is deselected, the CMOS standby current is less
than 100 µA. Device endurance is such that any sector can typically be written to in
excess of 10,000 times.
Pin Configurations
Pin Name
A0 - A17
CE
OE
WE
I/O0 - I/O7
NC
Function
Addresses
Chip Enable
Output Enable
Write Enable
Data Inputs/Outputs
No Connect
DIP Top View
NC
A16
A15
A12
A7
A6
A5
A4
A3
A2
A1
A0
I/O0
I/O1
I/O2
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
VCC
WE
A17
A14
A13
A8
A9
A11
OE
A10
CE
I/O7
I/O6
I/O5
I/O4
I/O3
TSOP Top View
Type 1
A11
A9
A8
A13
A14
A17
WE
VCC
NC
A16
A15
A12
A7
A6
A5
A4
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
OE
A10
CE
I/O7
I/O6
I/O5
I/O4
I/O3
GND
I/O2
I/O1
I/O0
A0
A1
A2
A3
PLCC Top View
4
3
2
1
32
31
30
A12
A15
A16
NC
VCC
WE
A17
I/O1
I/O2
GND
I/O3
I/O4
I/O5
I/O6
14
15
16
17
18
19
20
A7
A6
A5
A4
A3
A2
A1
A0
I/O0
5
6
7
8
9
10
11
12
13
29
28
27
26
25
24
23
22
21
A14
A13
A8
A9
A11
OE
A10
CE
I/O7
Rev. 0291N–FLASH–07/02
1
To allow for simple in-system reprogrammability, the AT29C020 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 an EPROM. Reprogramming the
AT29C020 is performed on a sector basis; 256 bytes of data are loaded into the device and
then simultaneously programmed.
During a reprogram cycle, the address locations and 256 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 sector and then program the latched data using
an internal control timer. The end of a program cycle can be detected by DATA polling of I/O7.
Once the end of a program cycle has been detected, a new access for a read or program can
begin.
Block Diagram
Device
Operation
READ:
The AT29C020 is accessed like an EPROM. 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:
Byte loads are used to enter the 256 bytes of a sector to be programmed or
the software codes for data protection. A byte load is performed by applying a low pulse on the
WE or CE input with CE or WE low (respectively) 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 WE.
PROGRAM:
The device is reprogrammed on a sector basis. If a byte of data within a sector
is to be changed, data for the entire sector must be loaded into the device. Any byte that is not
loaded during the programming of its sector will be indeterminate. Once the bytes of a sector
are loaded into the device, they are simultaneously programmed during the internal program-
ming 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 tran-
sition on WE (or CE) within 150 µs of the low-to-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. A8 to A17 specify the
sector address. The sector address must be valid during each high-to-low transition of WE (or
CE). A0 to A7 specify the byte address within the sector. 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
WC
, a read operation will effectively be a polling operation.
2
AT29C020
0291N–FLASH–07/02
AT29C020
SOFTWARE DATA PROTECTION:
A software controlled data protection feature is avail-
able on the AT29C020. 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 com-
mands 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 sector pro-
gram 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 pro-
tection feature; however, the software feature will guard against inadvertent program cycles
during power transitions.
After setting SDP, any attempt to write to the device without the 3-byte command sequence
will start the internal write timers. No data will be written to the device; however, for the dura-
tion of t
WC
, a read operation will effectively be a polling operation.
After the software data protection’s 3-byte command code is given, a sector of data is loaded
into the device using the sector program timing specifications.
HARDWARE DATA PROTECTION:
Hardware features protect against inadvertent pro-
grams to the AT29C020 in the following ways: (a) V
CC
sense – if V
CC
is below 3.8V (typical),
the program function is inhibited; (b) V
CC
power on delay – once V
CC
has reached the V
CC
sense level, the device will automatically time out 5 ms (typical) before programming; (c) Pro-
gram inhibit – holding any one of OE 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 pro-
gram cycle.
PRODUCT IDENTIFICATION:
The product identification mode identifies the device and
manufacturer as Atmel. It may be accessed by hardware or software operation. The hardware
operation mode can be used by an external programmer to identify the correct programming
algorithm for the Atmel product. In addition, users may wish to use the software product identi-
fication mode to identify the part (i.e. using the device code), and have the system software
use the appropriate sector size for program operations. In this manner, the user can have a
common board design for 256K to 4-megabit densities and, with each density’s sector size in
a memory map, have the system software apply the appropriate sector size.
For details, see Operating Modes (for hardware operation) or Software Product Identification.
The manufacturer and device code is the same for both modes.
DATA POLLING:
The AT29C020 features DATA polling to indicate the end of a program
cycle. During a program cycle an attempted read of the last byte loaded will result in the com-
plement 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 polling may begin at any time during
the program cycle.
TOGGLE BIT:
In addition to DATA polling the AT29C020 provides another method for deter-
mining 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. Examin-
ing 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 6-byte soft-
ware code. Please see Software Chip Erase application note for details.
3
0291N–FLASH–07/02
BOOT BLOCK PROGRAMMING LOCKOUT:
The AT29C020 has two designated memory
blocks that have a programming lockout feature. This feature prevents programming of data in
the designated block once the feature has been enabled. Each of these blocks consists of 8K
bytes; the programming lockout feature can be set independently for either block. While the
lockout feature does not have to be activated, it can be activated for either or both blocks.
These two 8K memory sections are referred to as
boot blocks
. Secure code which will bring up
a system can be contained in a boot block. The AT29C020 blocks are located in the first 8K
bytes of memory and the last 8K bytes of memory. The boot block programming lockout fea-
ture can therefore support systems that boot from the lower addresses of memory or the
higher addresses. Once the programming lockout feature has been activated, the data in that
block can no longer be erased or programmed; data in other memory locations can still be
changed through the regular programming methods. To activate the lockout feature, a series
of seven program commands to specific addresses with specific data must be performed.
Please see Boot Block Lockout Feature Enable Algorithm.
If the boot block lockout feature has been activated on either block, the chip erase function will
be disabled.
BOOT BLOCK LOCKOUT DETECTION:
A software method is available to determine
whether programming of either boot block section is locked out. See Software Product Identifi-
cation Entry and Exit sections. When the device is in the software product identification mode,
a read from location 00002H will show if programming the lower address boot block is locked
out while reading location 3FFF2H will do so for the upper boot block. If the data is FE, the cor-
responding block can be programmed; if the data is FF, the program lockout feature has been
activated and the corresponding block cannot be programmed. The software product identifi-
cation exit mode should be used to return to standard operation.
Absolute Maximum Ratings*
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
with Respect to Ground ...................................-0.6V to +13.5V
*NOTICE:
Stresses beyond those listed under “Absolute
Maximum Ratings” may cause permanent dam-
age 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.
4
AT29C020
0291N–FLASH–07/02
AT29C020
DC and AC Operating Range
AT29C020-70
Operating
Temperature (Case)
V
CC
Power Supply
Note:
Com.
Ind.
0°C - 70°C
-40°C - 85°C
5V
±
10%
Not recommended for New Designs.
AT29C020-90
0°C - 70°C
-40°C - 85°C
5V
±
10%
AT29C020-10
0°C - 70°C
-40°C - 85°C
5V
±
10%
AT29C020-12
0°C - 70°C
-40°C - 85°C
5V
±
10%
AT29C020-15
0°C - 70°C
-40°C - 85°C
5V
±
10%
Operating Modes
Mode
Read
Program
(2)
5V Chip Erase
Standby/Write Inhibit
Program Inhibit
Program Inhibit
Output Disable
Product Identification
Hardware
V
IL
V
IL
V
IH
A1 - A17 = V
IL
, A9 = V
H
,
(3)
A0 = V
IL
A1 - A17 = V
IL
, A9 = V
H
, A0 = V
IH
Software
(5)
A0 = V
IL
A0 = V
IH
Notes:
1.
2.
3.
4.
5.
X can be V
IL
or V
IH
.
Refer to AC Programming Waveforms.
V
H
= 12.0V
±
0.5V.
Manufacturer Code: 1F, Device Code: DA.
See details under Software Product Identification Entry/Exit.
Manufacturer Code
(4)
Device Code
(4)
Manufacturer Code
(4)
Device Code
(4)
CE
V
IL
V
IL
V
IL
V
IH
X
X
X
OE
V
IL
V
IH
V
IH
X
(1)
X
V
IL
V
IH
WE
V
IH
V
IL
V
IL
X
V
IH
X
X
High Z
Ai
Ai
Ai
Ai
X
High Z
I/O
D
OUT
D
IN
DC Characteristics
Symbol
I
LI
I
LO
I
SB1
Parameter
Input Load Current
Output Leakage Current
V
CC
Standby Current CMOS
Condition
V
IN
= 0V to V
CC
V
I/O
= 0V to V
CC
CE = V
CC
- 0.3V to V
CC
Com.
Ind.
I
SB2
I
CC
V
IL
V
IH
V
OL
V
OH1
V
OH2
V
CC
Standby Current TTL
V
CC
Active Current
Input Low Voltage
Input High Voltage
Output Low Voltage
Output High Voltage
Output High Voltage CMOS
I
OL
= 2.1 mA
I
OH
= -400 µA
I
OH
= -100 µA; V
CC
= 4.5V
2.4
4.2
2.0
0.45
CE = 2.0V to V
CC
f = 5 MHz; I
OUT
= 0 mA
Min
Max
10
10
100
300
3
40
0.8
Units
µA
µA
µA
µA
mA
mA
V
V
V
V
V
5
0291N–FLASH–07/02
京公网安备 11010802033920号
EEWORLD
