Datasheet 28C256ATC-1, 28C256ASM-4, 28C256ASM-3, 28C256ASM-2, 28C256ASM-1 Datasheet (Turbo IC)

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HIGH SPEED CMOS

256K ELECTRICALLY ERASABLE PROGRAMMABLE ROM

32K X 8 BIT EEPROM

ADDRESSES (A0 - A14)

The Addresses are used to select an 8 bits memory location during a write or read operation.

OUTPUT ENABLE (OE)

The Output Enable input activates the output buffers during the read operations.

CHIP ENABLES (CE)

The Chip Enable input must be low to enable all read/write operation on the device. By setting CE high, the device is disabled and the power consumption is extremely low with the standby current below 200 µA.

FEATURES:

• 120 ns Access Time

• Automatic Page Write Operation Internal Control Timer Internal Data and Address Latches for 64 Bytes

• Fast Write Cycle Times Byte or Page Write Cycles: 10 ms Time to Rewrite Complete Memory: 5 sec T ypical Byte Write Cycle Time: 160 µsec

• Software Data Protection

• Low P ower Dissipation 50 mA Active Current 200 µA CMOS Standby Current

• Direct Microprocessor End of Write Detection Data Polling

• High Reliability CMOS Technology with Self Redundant

EEPROM Cell

Endurance: 100,000 Cycles Data Retention: 10 Years

• TTL and CMOS Compatible Inputs and Outputs

• Single 5 V ± 10% P ow er Supply f or Read and

Programming Operations

• JEDEC Approved Byte-Write Pinout

DESCRIPTION:

The Turbo IC 28C256A is a 32K X 8 EEPROM fabricated with Turbo’s proprietary, high reliability, high performance CMOS technology . The 256K bits of memory are organized as 32K by 8 bits. The device offers access time of 120 ns with power dissipation below 250 mW.

The 28C256A has a 64-bytes page write operation, enabling the entire memory to be typically written in less than 5.0 seconds. During a write cycle, the address and 1 to 64 b ytes of data are internally latched, freeing the address and data bus for other microprocessor operations. The programming process is automatically controlled by the device using an internal control timer. Data polling on one or all I/O can be used to detect the end of a programming cycle. In addition, the 28C256A includes an user-optional software data write mode offering additional protection against unwanted (false) write. The de vice utiliz es an error protected self redundant cell for extended data retention and endur ance.

WRITE ENABLE (WE)

The Write Enable input initiates the writing of data into the memory.

DATA INPUT/OUTPUT (I/O0-I/O7)

Data Input/Output pins are used to read data out of the memory or to write Data into the memory.

PIN DESCRIPTION

6 7 8 9 10 11 12 13

303132

A8 A9 A11 NC OE A10 CE I/O7 I/O6

A6 A5 A4 A3 A2 A1 A0

I/O0

I/O1

I/O2

GNDNCI/O3

I/O4

I/O5

A12

A7 A14NCVCCWEA13

32 pins PLCC

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

28A14

A12

A7 A6 A5 A4 A3 A2 A1

A0 I/O0 I/O1 I/O2

GND

VCC WE A13 A8 A9 A11 OE A10 CE I/O7 I/O6 I/O5 I/O4 I/O3

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

28A14

A12

A7 A6 A5 A4 A3 A2 A1

A0 I/O0 I/O1 I/O2

GND

VCC WE A13 A8 A9 A11 OE A10 CE I/O7 I/O6 I/O5 I/O4 I/O3

A10 I/O7 I/O5 I/O3 I/O2 I/O0 A1

I/O1

GND

I/O4

I/O6

A13

VCC

A12

A6 A4

A14

A11

28 pins PDIP

28 pins SOIC (SOG)

28 pins TSOP

29 28 27 26 25 24 23 22

Turbo IC, Inc.

28C256A

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a.) Software Write Protect Enable

A sequence of three dummy data writes to the memory will activate internal EEPROM fuses during the first page write cycle. These EEPROM fuses will reject any write attempts of new pages of data unless the three dummy data writes are repeated at the beginning of any page writes. The timing f or the dummy data and addresses m ust be the same as for a normal write operation. A violation of the three steps write protect sequence in data or address timing and content will abort the procedure and reset the device to the starting point condition.

Note: After the three dummy data writes, at least one page load/ write cycle must be performed. If no additional page data is added to the three dummy data writes, the software write protect will not be enabled until the next write, which will not be protected.

T able 1 sho ws the required procedure for enab ling the software write protect:

Step Mode Address A14-A0 Data I/O 7-0 1 Page Write 5555 Hex AA Hex 2 Page Write 2AAA Hex 55 Hex 3 Page Write 5555 Hex A0 Hex 4-67 Page Write Address Data

b.) Software Write Protect Disable

The software algorithm of 28C256A includes a six steps sequence of dummy data writing to disable the software write protect feature described in a.). The six steps write sequence shown in Table 2 must be performed at the beginning of a page write cycle. A violation of the six steps write sequence in data or address timing and content will abort the procedure and reset the chip to the starting point condition. After a page write cycle including the six steps write sequence has been performed, the 28C256A does not require the use of three dummy data writes described in a.) for the following page write cycle. The device is at the software write protect disabled state.

Note: After the six dummy data writes, at least one page load/ write cycle must be performed. If no additional page data is added to the six dummy data writes, the software write pr otect disable will not be activated. Table 2 shows the required procedure for dis-

abling the software write protect: Step Mode Address A14-A0 Data I/O 7-0

1 Page Write 5555 Hex AA Hex 2 Page Write 2AAA Hex 55 Hex 3 Page Write 5555 Hex 80 Hex 4 Page Write 5555 Hex AA Hex 5 Page Write 2AAA Hex 55 Hex 6 Page Write 5555 Hex 20 Hex 7-70 Page Write Address Data

c.) Software Chip Clear

The software algorithm of 28C256A includes a sequence of six steps dummy data writing to perform a chip clear operation. Table 3 shows the six steps write sequence to perform the software chip clear operation:

Step Mode Address A14-A0 Data I/O 7-0 1 Page Write 5555 Hex AA Hex 2 Page Write 2AAA Hex 55 Hex 3 Page Write 5555 Hex 80 Hex 4 Page Write 5555 Hex AA Hex 5 Page Write 2AAA Hex 55 Hex 6 Page Write 5555 Hex 10 Hex

At the end of the six steps write sequence shown in Table 3, the device automatically activates its internal timer to control the chip

DEVICE OPERA TION

READ:

The 28C256A is accessed like a static RAM. Read operations are initiated by both CE and OE going low and terminated by either CE or OE returning high. The outputs are at the high impedance state whenever CE or OE returns high. The two line control architecture gives designers flexibility in preventing bus contention.

WRITE:

A write cycle is initiated when CE and WE are low and OE is high. The address is latched internally on the falling edge of CE or WE whichever occurs last. The data is latched b y the rising edge of CE or WE whiche ver occurs first. Once a byte write cycle has been started, the inter nal timer automatically generates the write sequence to the completion of the write operation.

P AGE WRITE OPERATION:

The page write operation of 28C256A allows one to 64 bytes of data to be serially loaded into the device and then simultaneously written into memory during the internally generated wr ite cycle. After the first byte has been loaded, successive bytes of data may be loaded until the full page of 64 bytes is loaded. Each new byte to be written must be loaded within 200 µs of the previously loaded byte. The page address defined by the addresses A6-A14 is latched by the first CE or WE f alling edge which initiates a writing cycle and they will stay latched until the completion of the page write. Any changes in the page addresses during the load-write cycle will not affect the initially latched page addresses. Addresses A0 A5 are used to define which bytes will be loaded and written within the 64 bytes page. The bytes may be loaded in any order that is convenient to the user. The content of a loaded byte may be altered at any time during the loading cycle if the maximum allowed byte-load time (200 µs) is not exceeded. Only loaded bytes within the page will be written; no rewriting will occur to the non-selected bytes in the page.

DATA POLLING:

The 28C256A features DATA POLLING to indicate the completion of a write cycle to the host system. During a byte or page write cycle, an attempted read of the last byte loaded into the page will result in the complement of the loaded byte on all outputs I/O0 - I/O7 (i.e. loaded data 01010110, read data 10101001). Data P olling f eature may be used by an attempted read on one or more outputs (whatever is convenient for the system developer). Once the write cycle has been completed, true data is valid on all outputs and the next cycle may be started.

DATA PROTECTION:

The 28C256A has three hardware features to protect the written content of the memory against inadvertent writes :

a.) Vcc threshold detector: If Vcc is below 2.5 V, the wr ite capabilities of the chip is inhibited for whatever input conditions. b.) Noise protection: A WE, OE, or CE pulse less than 10 ns in width is not able to initiate a write cycle. c.) Write inhibit: Holding OE at low, or CE at high, or WE at high inhibits the write cycle.

SOFTWARE WRITE PROTECTION:

The 28C256A offers a software controlled data write protection feature. The device is delivered to the user with the software data write protection DISABLED; i.e. the device will go to the data write operation as long as Vcc exceeds 2.5 V and CE, WE, and OE inputs are set at write mode levels. The 28C256A can be automatically protected against an accidental write operation during power-up or power-down without any external circuitry by enabling the software data write protection features. This f eatures is enabled after the first write cycle which includes the software algorithm. After this operation is done, the data write function of the device may be performed only if every page write cycle is preceded by the software algorithm. The device will maintain its software protect feature f or the rest of its life unless that the software algorithm for disabling the protection is implemented.

SOFTWARE ALGORITHM:

The 28C256A has an internal register for the software algorithm which enables the memory to provide the user with additional features:

Turbo IC, Inc.

28C256A

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erase cycle; typically takes 20 msec. After a software chip clear operation has been completed, all 256K bit locations of memory show high level at read operation mode.

d.) Software Autoclear Disable Mode

This software algorithm disables the internal automatic clear before write cycle. Table 4 shows the six steps needed to perf orm the autoclear disable mode:

Page write operation using the software autoclear disable mode will reduce programming time to typically 5 msec. The page write using software autoclear disable mode is usually used after a chip clear or a software chip clear operation. At the end of the six steps sequence, the autoclear before write is disabled and will stay that wa y unless a power-down occurs or the software autoclear enable procedure is initiated.

e.) Software Autoclear Enable Mode

Automatic page clear before page write can be restored to 28C256A either by Vcc power-down or by software autoclear enable mode. Table 5 shows the six steps page write procedure needed to enable software autoclear mode:

Symbol Parameter Condition Min Max Units

Icc Active Vcc CE=OE=Vil; All I/O 50 (C) mA

Current Open, Min Read or 70 (I) mA

Write Cycle Time 90 (M) mA

Isb1 CMOS CE=Vcc-0.3 V to 200 (C) µA

Standby Vcc+1 V 300 (I&M) µA Current

Isb2 TTL Standby CE=Vih, OE=Vil, 3 mA

Current All I/O Open, Other

Inputs=Vcc Max Vin=Vcc Max

Iil Input 1 µA

Leakage Current

Iol Output 10 µA

Leakage Current

Vil Input Low -0.1 -0.8 V

Voltage

Vih Input High 2 Vcc+0.3 V

Voltage

Vo l Output Low Iol=2.1 mA 0.45 V

Voltage

Voh Output High Ioh=-0.45 mA 2.4 V

Voltage

D.C. CHARACTERISTICS

Turbo IC, Inc.

28C256A

ABSOLUTE MAXIMUM STRESS RANGES *

TEMPERATURE

Storage: -65° C to 150° C Under Bias: -55° C to 125° C

ALL INPUT OR OUTPUT VOLTAGES

with respect to Vss +6 V to -0.3 V

“Absolute Maximum Ratings” ma y cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

RECOMMENDED OPERATING CONDITIONS Temperature Range: Commercial: 0° C to 70° C

Industrial: -40° C to 85° C Military: -55° C to 125° C

Vcc Supply Voltage:5 V ± 10%

Endurance: 100,000 Cycles/Byte (Typical) Data Retention: 10 Years

A.C. CHARACTERISTICS - READ OPERATION

28C256A-1 28C256A-2 28C256A-3 28C256A-4

Symbol Parameters Min Max Min Max Min Max Min MaxUnit tacc Address to 120 150 200 250 ns

Output Delay

tce CE to Output 120 150 200 250 ns

Delay toe OE to Output 70 90 110 150 ns tdf OE to Output 0 40 0 60 0 90 0 90 ns

In High Z toh Output Hold 0000ns

from Address

Changes, Chip

Enable or

Output Enable

Whichever

Occurs First

A.C. Read Wave Forms

A.C. TEST CONDITIONS

Output Load : 1 TTL Load and Cl=100 pF Input Rise and Fall Times : < 10 ns Input Pulse Level : 0 V to 3 V Timing Measurement Reference Level : 1.5 V

tacc

ADDRESS VALIDADDRESS

OUTPUT HIGH-Z

toe

tce

tdf

toh

OUTPUT VALID

HIGH-Z

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TURBO IC PRODUCTS AND DOCUMENTS

1. All documents are subject to change without notice. Please contact Turbo IC for the latest revision of documents.

2. Turbo IC does not assume any responsibility for any damage to the user that may result from accidents or operation under abnormal conditions.

3. Turbo IC does not assume any responsibility for the use of any circuitry other than what embodied in a Turbo IC product. No other circuits, patents, licenses are implied.

4. Turbo IC products are not authorized for use in life support systems or other critical systems where component failure may endanger life. System designers should design with error detection and correction, redundancy and back-up features.

A.C. WRITE CHARACTERISTICS

Symbol Parameter Min Max Units tas Address Set-up Time 20 ns tah Address Hold Time 100 ns tcs Write Set-up Time 0 ns tch Write Hold Time 0 ns tcw CE Pulse Width 150 ns twp WE Pulse Width 150 ns toes OE Set-up Time 20 ns toeh OE Hold Time 20 ns tds Data Set-up Time 50 ns tdh Data Hold Time 0 ns tdh Data Hold (28C256A-4 ONLY) 10 ns tblc Byte Load Cycle 0.2 200 µs tlp Last Byte Loaded to Data

Polling Output 500 µ s twc Write Cycle Time 10 m s twc Write Cycle Time (IND & MIL) 15 ms

Part Numbers & Order Inf ormation

28C256APC-2

Speed

-1 120 ns

-2 150 ns

-3 200 ns

-4 250 ns

Temperature C -Commercial I -Industrial M -Military

Package J -PLCC

P -PDIP

S -SOIC T -TSOP

Turbo IC, Inc. 2365 Paragon Drive, Suite I, San Jose, CA 95131 Phone: 408-392-0208 Fax: 408-392-0207

See us at www.turbo-ic.com

32K x 8 EEPROM

Page Mode Write Wave Form

PAGE MODE WRITE CHARACTERISTICS

Symbol Parameter Min Max Unit

twc Write Cycle Time 10 ms tas Address Set-up Time 20 n s tah Address Hold Time 100 ns tds Data Set-up Time 50 ns tdh Data Hold Time 0 ns twp Write Pulse Width 150 ns tblc Byte Load Cycle Time 0.2 200 µ s

Chip Clear Wave Form

The content of the 28C256A may be altered to HIGH by the use of the Chip Clear operation. By setting CE to low, OE to 12 volts, and WE to low, the entire memory can be cleared (written HIGH) within 20 ms. The Chip Clear operation is a latch operation mode. After the Chip Clear starts, the internal chip timer takes over and completes the clear without CE, OE and WE being held active.

A.C. Write Characteristics CE-Controlled

A.C. Write Characteristics WE-Controlled

ADDRESS

DATA

toes

tas

tcs tah

toeh

tch

tcw

tds

tblc

twc

tdh

HIGH-Z

DATA VALID

HIGH-Z

VALID

ADDRESS

DATA

toes

tas

tcs tah

toeh

tch

twp

tds

tblc

twc

tdh

HIGH-Z

DATA VALID

HIGH-Z

VALID

A0-A5

DATA

twp

tblc

tah

tas

tds

tdh

BYTE-0

BYTE-1

BYTE-2

AD-VALID

ts= 20 ns tp= 200 ns th= 20 ns VH=12.0 V±0.5V

VIH

VIL

VIH

VIL

Turbo IC, Inc.

28C256A

Rev . 4.0 - 10/28/01