The BM29F400 is an 4 Megabit, 5.0 volt-only CMOS Flash memory device organized as a 512 Kbytes of 8-bits each, or 256 Kbytes of 16 bits each. The device is offered in standard 48-pin TSOP package. It is designed to be programmed and erased in-system with a 5.0 volt power-supply and can also be reprogrammed in standard EPROM programmers. With access times of 90 nS, 120 nS, and 150 nS, the BM29F400 has separate chip enable CE , write enable WE , and output enable OE controls. BMI's memory devices reliably store memory data even after 100,000 program and erase cycles. The BM29F400 is entirely pin and command set compatible with the JEDEC standard for 4 Megabit Flash memory devices. Commands are written to the command register using standard microprocessor write timings. Register contents serve as input to an internal state-machine which controls the erase and programming circuitry. Write cycles also internally latch addresses and data needed for the programming and erase operations. The BM29F400 is programmed by executing the program command sequence. This will start the internal byte/word programming algorithm that automatically times the program pulse width and also verifies the proper cell margin. Erase is accomplished by executing either the sector erase or chip erase command sequence. This will start the internal erasing algorithm that automatically times the erase pulse width and also verifies the proper cell margin. No preprogramming is required prior to execution of the internal erase algorithm. Sectors of the BM29F400 Flash memory array are electrically erased via Fowler-Nordheim tunneling. Bytes/words are programmed one byte/word at a time using a hot electron injection mechanism. The BM29F400 features a sector erase architecture. The device memory array is divided into one 16 Kbytes, two 8 Kbytes, one 32 Kbytes, and seven 64 Kbytes. Sectors can be erased individually or in groups without affecting the data in other sectors. Multiple sector erase and full chip erase capabilities add flexibility to altering the data in the device. To protect this data from accidental program and erase, the device also has a sector protect function. This function hardware write protects the selected sector(s). The sector protect and sector unprotect features can be enabled in a PROM programmer.