AT28C256 Features • • • • • • • • • • • Fast Read Access Time - 150 ns Automatic Page Write Operation Internal Address and Data Latches for 64-Bytes Internal Control Timer Fast Write Cycle Times Page Write Cycle Time: 3 ms or 10 ms Maximum 1 to 64-Byte Page Write Operation Low Power Dissipation 50 mA Active Current 200 µA CMOS Standby Current Hardware and Software Data Protection DATA Polling for End of Write Detection High Reliability CMOS 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 256K (32K x 8) Paged CMOS E2PROM Description The AT28C256 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 device offers access times to 150 ns with power dissipation of just 440 mW. When the device is deselected, the CMOS standby current is less than 200 µA. (continued) Pin Configurations TSOP Top View Pin Name Function A0 - A14 Addresses CE Chip Enable OE Output Enable WE Write Enable I/O0 - I/O7 Data Inputs/Outputs NC No Connect DC Don’t Connect PGA Top View LCC, PLCC Top View Note: PLCC package pins 1 and 17 are DON’T CONNECT. AT28C256 CERDIP, PDIP, FLATPACK, SOIC Top View 0006F 2-217 Description (Continued) The AT28C256 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 writing of up to 64-bytes simultaneously. During a write cycle, the addresses and 1 to 64-bytes of data are internally latched, freeing the address 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 28C256 has additional features to ensure high quality and manufacturability. The device utilizes internal error correction 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 E2PROM for device identification or tracking. Block Diagram 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 VCC + 0.6V Voltage on OE and A9 with Respect to Ground ................... -0.6V to +13.5V 2-218 AT28C256 *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. AT28C256 Device Operation READ: The AT28C256 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 cycle. 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. 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 tWC, a read operation will effectively be a polling operation. PAGE WRITE: The page write operation of the AT28C256 allows 1 to 64-bytes of data to be written 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 (tBLC) of the previous byte. If the tBLC limit is exceeded the AT28C256 will cease accepting data and commence the internal 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. 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 AT28C256 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 complement 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 AT28C256 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. Reading the toggle bit may begin at any time during the write cycle. DATA PROTECTION: If precautions are not taken, inadvertent writes may occur during transitions 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 AT28C256 in the following ways: (a) VCC sense - if VCC is below 3.8V (typical) the write function is inhibited; (b) VCC power-on delay - once VCC 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 AT28C256. When enabled, the software data protection (SDP), will prevent inadvertent writes. The SDP feature may be enabled or disabled by the user; the AT28C256 is shipped from Atmel with SDP disabled. SDP is enabled by the host system issuing a series of three write commands; 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 tWC the entire AT28C256 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 AT28C256. This is done by preceding the data to be written by the same 3-byte command sequence used to enable SDP. Once set, SDP will remain active unless the disable command sequence is issued. Power transitions do not disable SDP and SDP will protect the AT28C256 during power-up and power-down conditions. All command sequences must conform to the page write timing specifications. 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 3-byte command sequence will start the internal write timers. No data will be written to the device; however, for the duration of tWC, read operations will effectively be polling operations. (continued) 2-219 Device Operation (Continued) DEVICE IDENTIFICATION: A n e x t r a 6 4 - b y t e s o f E2PROM 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. DC and AC Operating Range AT28C256-15 AT28C256-20 AT28C256-25 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 -55°C - 125°C -55°C - 125°C 5V ± 10% 5V ± 10% 5V ± 10% 5V ± 10% Com. Operating Temperature (Case) VCC Power Supply AT28C256-35 Operating Modes Mode CE OE WE I/O Read VIL VIL VIH DOUT VIL VIH VIL DIN VIH (1) Write (2) Standby/Write Inhibit X X High Z Write Inhibit X X VIH Write Inhibit X VIL X Output Disable X VIH X High Z VIL High Z Chip Erase VH VIL (3) 3. VH = 12.0V ± 0.5V. Notes: 1. X can be VIL or VIH. 2. Refer to AC Programming Waveforms. DC Characteristics Symbol Parameter Condition Min Max Units ILI Input Load Current VIN = 0V to VCC + 1V 10 µA ILO Output Leakage Current VI/O = 0V to VCC 10 µA ISB1 VCC Standby Current CMOS CE = VCC - 0.3V to VCC + 1V Com., Ind. 200 µA Mil. 300 µA ISB2 VCC Standby Current TTL CE = 2.0V to VCC + 1V 3 mA ICC VCC Active Current f = 5 MHz; IOUT = 0 mA 50 mA VIL Input Low Voltage 0.8 V VIH Input High Voltage VOL Output Low Voltage IOL = 2.1 mA VOH Output High Voltage IOH = -400 µA 2-220 AT28C256 2.0 V .45 2.4 V V AT28C256 AC Read Characteristics AT28C256-15 AT28C256-20 AT28C256-25 AT28C256-35 Symbol Parameter tACC Min Max Min Max Min Max Min Max Units Address to Output Delay 150 200 250 350 ns tCE (1) CE to Output Delay 150 200 250 350 ns tOE (2) OE to Output Delay 0 70 0 80 0 100 0 100 ns tDF (3, 4) CE or OE to Output Float 0 50 0 55 0 60 0 70 ns Output Hold from OE, CE or Address, whichever occurred first 0 tOH 0 0 0 ns AC Read Waveforms (1, 2, 3, 4) Notes: 1. CE may be delayed up to tACC - tCE after the address transition without impact on tACC. 2. OE may be delayed up to tCE - tOE after the falling edge of CE without impact on tCE or by tACC - tOE after an address change without impact on tACC. 3. tDF is specified from OE or CE whichever occurs first (CL = 5 pF). 4. This parameter is characterized and is not 100% tested. Input Test Waveforms and Measurement Level Output Test Load tR, tF < 5ns Pin Capacitance (f = 1 MHz, T = 25°C) (1) CIN COUT Note: Typ Max Units Conditions 4 6 pF VIN = 0V 8 12 pF VOUT = 0V 1. This parameter is characterized and is not 100% tested. 2-221 AC Write Characteristics Symbol Parameter tAS, tOES Address, OE Set-up Time 0 ns tAH Address Hold Time 50 ns tCS Chip Select Set-up Time 0 ns tCH Chip Select Hold Time 0 ns tWP Write Pulse Width (WE or CE) 100 ns tDS Data Set-up Time 50 ns tDH, tOEH Data, OE Hold Time 0 ns Time to Data Valid tDV Note: 1. NR = No Restriction AC Write Waveforms WE Controlled CE Controlled 2-222 AT28C256 Min NR (1) Max Units AT28C256 Page Mode Characteristics Symbol Parameter Min Max Units tWC Write Cycle Time AT28C256 10 ms AT28C256F 3.0 ms tAS Address Set-up Time 0 ns tAH Address Hold Time 50 ns tDS Data Set-up Time 50 ns tDH Data Hold Time 0 ns tWP Write Pulse Width 100 ns tBLC Byte Load Cycle Time tWPH Write Pulse Width High 150 50 µs ns Page Mode Write Waveforms (1, 2) Notes: 1. A6 through A14 must specify the same page address during each high to low transition of WE (or CE). 2. OE must be high only when WE and CE are both low. Chip Erase Waveforms tS = tH = 5 µsec (min.) tW = 10 msec (min.) VH = 12.0V ± 0.5V 2-223 Software Data Protection Enable Algorithm (1) Software Data Protection Disable Algorithm (1) LOAD DATA AA TO ADDRESS 5555 LOAD DATA AA TO ADDRESS 5555 LOAD DATA 55 TO ADDRESS 2AAA LOAD DATA 55 TO ADDRESS 2AAA LOAD DATA A0 TO ADDRESS 5555 LOAD DATA 80 TO ADDRESS 5555 WRITES ENABLED (2) LOAD DATA AA TO ADDRESS 5555 LOAD DATA XX TO ANY ADDRESS (4) LOAD LAST BYTE TO LAST ADDRESS ENTER DATA PROTECT STATE Notes for software program code: 1. Data Format: I/O7 - I/O0 (Hex); Address Format: A14 - A0 (Hex). 2. Write Protect state will be activated at end of write even if no other data is loaded. 3. Write Protect state will be deactivated at end of write period even if no other data is loaded. 4. 1 to 64-bytes of data are loaded. LOAD DATA 55 TO ADDRESS 2AAA LOAD DATA 20 TO ADDRESS 5555 EXIT DATA PROTECT STATE (3) LOAD DATA XX TO ANY ADDRESS (4) LOAD LAST BYTE TO LAST ADDRESS Software Protected Write Cycle Waveforms (1, 2) Notes: 1. A6 through A14 must specify the same page address during each high to low transition of WE (or CE) after the software code has been entered. 2. OE must be high only when WE and CE are both low. 2-224 AT28C256 AT28C256 Data Polling Characteristics (1) Symbol Parameter Min Typ Max Units tDH Data Hold Time 0 ns tOEH OE Hold Time 0 ns tOE OE to Output Delay (2) tWR Write Recovery Time ns 0 Notes: 1. These parameters are characterized and not 100% tested. ns 2. See AC Read Characteristics. Data Polling Waveforms Toggle Bit Characteristics (1) Symbol Parameter tDH Data Hold Time tOEH OE Hold Time Min Typ Max 10 ns 10 ns (2) tOE OE to Output Delay tOEHP OE High Pulse tWR Write Recovery Time Units ns 150 ns 0 ns Notes: 1. These parameters are characterized and not 100% tested. 2. See AC Read Characteristics. Toggle Bit Waveforms (1, 2, 3) 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. 2-225 2-226 AT28C256 AT28C256 Ordering Information (2) tACC ICC (mA) (ns) Active Standby 150 50 0.2 200 250 Ordering Code Package AT28C256(E,F)-15JC AT28C256(E,F)-15PC AT28C256(E,F)-15SC AT28C256(E,F)-15TC 32J 28P6 28S 28T Commercial (0°C to 70°C) AT28C256(E,F)-15JI AT28C256(E,F)-15PI AT28C256(E,F)-15SI AT28C256(E,F)-15TI 32J 28P6 28S 28T Industrial (-40°C to 85°C) Operation Range 50 0.3 AT28C256(E,F)-15DM/883 AT28C256(E,F)-15FM/883 AT28C256(E,F)-15LM/883 AT28C256(E,F)-15UM/883 28D6 28F 32L 28U Military/883C Class B, Fully Compliant (-55°C to 125°C) 50 0.2 AT28C256(E,F)-20JC AT28C256(E,F)-20PC AT28C256(E,F)-20SC AT28C256(E,F)-20TC 32J 28P6 28S 28T Commercial (0°C to 70°C) AT28C256(E,F)-20JI AT28C256(E,F)-20PI AT28C256(E,F)-20SI AT28C256(E,F)-20TI 32J 28P6 28S 28T Industrial (-40°C to 85°C) 50 0.3 AT28C256(E,F)-20DM/883 AT28C256(E,F)-20FM/883 AT28C256(E,F)-20LM/883 AT28C256(E,F)-20UM/883 28D6 28F 32L 28U Military/883C Class B, Fully Compliant (-55°C to 125°C) 50 0.2 AT28C256(E,F)-25JC AT28C256(E,F)-25PC AT28C256-W 32J 28P6 DIE Commercial (0°C to 70°C) AT28C256(E,F)-25JI AT28C256(E,F)-25PI 32J 28P6 Industrial (-40°C to 85°C) Military/883C Class B, Fully Compliant (-55°C to 125°C) 50 0.3 AT28C256(E,F)-25DM/883 AT28C256(E,F)-25FM/883 AT28C256(E,F)-25LM/883 AT28C256(E,F)-25UM/883 AT28C256(E,F)-35UM/883 28D6 28F 32L 28U 28U 50 0.2 AT28C256-W DIE Commercial (0°C to 70°C) (continued) 2-227 Ordering Information (Continued) tACC ICC (mA) (ns) Active Standby 150 (3) 50 0.35 50 200 (3) 250 (3) 0.35 Ordering Code Package 5962-88525 16 UX 5962-88525 16 XX 5962-88525 16 YX 5962-88525 16 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) 5962-88525 15 UX 5962-88525 15 XX 5962-88525 15 YX 5962-88525 15 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) 5962-88525 14 UX 5962-88525 14 XX 5962-88525 14 YX 5962-88525 14 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) 5962-88525 08 UX 5962-88525 08 XX 5962-88525 08 YX 5962-88525 08 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) 5962-88525 07 UX 5962-88525 07 XX 5962-88525 07 YX 5962-88525 07 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) 5962-88525 06 UX 5962-88525 06 XX 5962-88525 06 YX 5962-88525 06 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) Operation Range 50 0.35 5962-88525 12 UX 5962-88525 12 XX 5962-88525 12 YX 5962-88525 12 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) 50 0.35 5962-88525 04 UX 5962-88525 04 XX 5962-88525 04 YX 5962-88525 04 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) 50 0.35 5962-88525 13 UX 5962-88525 13 XX 5962-88525 13 YX 5962-88525 13 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) 5962-88525 11 UX 5962-88525 11 XX 5962-88525 11 YX 5962-88525 11 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) (continued) 2-228 AT28C256 AT28C256 Ordering Information (Continued) tACC ICC (mA) (ns) Active Standby 250 50 0.35 300 350 Ordering Code Package 5962-88525 05 UX 5962-88525 05 XX 5962-88525 05 YX 5962-88525 05 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) 5962-88525 03 UX 5962-88525 03 XX 5962-88525 03 YX 5962-88525 03 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) Operation Range 50 0.35 5962-88525 10 UX 5962-88525 10 XX 5962-88525 10 YX 5962-88525 10 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) 50 0.35 5962-88525 02 UX 5962-88525 02 XX 5962-88525 02 YX 5962-88525 02 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) 50 0.35 5962-88525 09 UX 5962-88525 09 XX 5962-88525 09 YX 5962-88525 09 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) 50 0.35 5962-88525 01 UX 5962-88525 01 XX 5962-88525 01 YX 5962-88525 01 ZX 28U 28D6 32L 28F Military/883C Class B, Fully Compliant (-55°C to 125°C) Notes: 1. Electrical specifications for these speeds are defined by Standard Microcircuit Drawing 5962-88525. 2. See Valid Part Number table below. 3. SMD specifies Software Data Protection feature for device type, although Atmel product supplied to every device type in the SMD is 100% tested for this feature. Valid Part Numbers The following table lists standard Atmel products that can be ordered. Device Numbers Speed Package and Temperature Combinations AT28C256 15 JC, JI, PC, PI, SC, SI, TC, TI, DM/883, FM/883, LM/883, UM/883 AT28C256E 15 JC, JI, PC, PI, SC, SI, TC, TI, DM/883, FM/883, LM/883, UM/883 AT28C256F 15 JC, JI, PC, PI, SC, SI, TC, TI, DM/883, FM/883, LM/883, UM/883 AT28C256 20 JC, JI, PC, PI, SC, SI, TC, TI, DM/883, FM/883, LM/883, UM/883 AT28C256E 20 JC, JI, PC, PI, SC, SI, TC, TI, DM/883, FM/883, LM/883, UM/883 AT28C256F 20 JC, JI, PC, PI, SC, SI, TC, TI, DM/883, FM/883, LM/883, UM/883 AT28C256 25 JC, JI, PC, PI, SC, SI, TC, TI, DM/883, FM/883, LM/883, UM/883 AT28C256E 25 JC, JI, PC, PI, SC, SI, TC, TI, DM/883, FM/883, LM/883, UM/883 AT28C256F 25 JC, JI, PC, PI, SC, SI, TC, TI, DM/883, FM/883, LM/883, UM/883 AT28C256 - W 2-229 Package Type 28D6 28 Lead, 0.600" Wide, Non-Windowed, Ceramic Dual Inline Package (Cerdip) 28F 28 Lead, Non-Windowed, Ceramic Bottom-Brazed Flat Package (Flatpack) 32J 32 Lead, Plastic J-Leaded Chip Carrier (PLCC) 32L 32 Pad, Non-Windowed, Ceramic Leadless Chip Carrier (LCC) 28P6 28 Lead, 0.600" Wide, Plastic Dual Inline Package (PDIP) 28S 28 Lead, 0.300" Wide, Plastic Gull Wing Small Outline (SOIC) 28T 28 Lead, Plastic Thin Small Outline Package (TSOP) 28U 28 Pin, Ceramic Pin Grid Array (PGA) W Die Options Blank Standard Device: Endurance = 10K Write Cycles; Write Time = 10 ms E High Endurance Option: Endurance = 100K Write Cycles F Fast Write Option: Write Time = 3 ms 2-230 AT28C256