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 256K (32K x 8) 50 mA Active Current 200 A CMOS Standby Current Paged Parallel Hardware and Software Data Protection DATA Polling for End of Write Detection EEPROM High Reliability CMOS Technology 4 5 Endurance: 10 or 10 Cycles Data Retention: 10 Years Single 5V 10% Supply AT28C256 CMOS and TTL Compatible Inputs and Outputs JEDEC Approved Byte-wide Pinout Full Military and Industrial Temperature Ranges Green (Pb/Halide-free) Packaging Option 1. 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. Manufac- tured with Atmels 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 A. 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. Atmels AT28C256 has additional features to ensure high quality and manufacturabil- ity. 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 EEPROM for device identification or tracking. 0006MPEEPR12/092. Pin Configurations 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 Dont Connect 2.3 32-pad LCC, 28-lead PLCC Top View 2.1 28-lead TSOP Top View OE 1 28 A10 A11 2 27 CE A6 5 29 A8 A9 3 26 I/O7 A5 6 28 A9 A8 4 25 I/O6 A4 7 27 A11 A13 5 24 I/O5 A3 8 26 NC WE 6 23 I/O4 A2 9 25 OE VCC 7 22 I/O3 A1 10 24 A10 A14 8 21 GND A0 11 23 CE A12 9 20 I/O2 NC 12 22 I/O7 A7 10 19 I/O1 I/O0 13 21 I/O6 A6 11 18 I/O0 A5 12 17 A0 A4 13 16 A1 A3 14 15 A2 Note: PLCC package pins 1 and 17 are Dont Connect. 2.4 28-lead Cerdip/PDIP/Flatpack/SOIC 2.2 28-lead PGA Top View Top View A14 1 28 VCC A12 2 27 WE A7 3 26 A13 A6 4 25 A8 A5 5 24 A9 A4 6 23 A11 A3 7 22 OE A2 8 21 A10 A1 9 20 CE A0 10 19 I/O7 I/O0 11 18 I/O6 I/O1 12 17 I/O5 I/O2 13 16 I/O4 GND 14 15 I/O3 2 AT28C256 0006MPEEPR12/09 I/O1 14 4 A7 I/O2 15 3 A12 GND 16 2 A14 DC 17 1 DC I/O3 18 32 VCC I/O4 19 31 WE I/O5 20 30 A13