A29L400A Series

The A29L400A is an 4Mbit, 3.0 volt-only Flash memory organized as 524,288 bytes of 8 bits or 262,144 words of 16
bits each. The 8 bits of data appear on I/O0 - I/O7; the 16 bits of data appear on I/O0~I/O15. The A29L400A is offered in 48- ball TFBGA, 44-pin SOP and 48-Pin TSOP packages. This device is designed to be programmed in-system with the standard system 3.0 volt VCC supply. Additional 12.0 volt VPP is not required for in-system write or erase operations. However, the A29L400A can also be programmed in standard EPROM programmers.

The A29L400A has the first toggle bit, I/O6, which indicates whether an Embedded Program or Erase is in progress, or it is in the Erase Suspend. Besides the I/O6 toggle bit, the A29L400A has a second toggle bit, I/O2, to indicate whether   the addressed sector is being selected for erase. The A29L400A also offers the ability to program in the Erase Suspend mode. The standard A29L400A offers access times of 70 and 90ns, allowing high-speed  icroprocessors to perate without wait states. To eliminate bus contention the device has separate chip enable (CE), write enable (WE ) and output enable (OE ) controls.

The device requires only a single 3.0 volt power supply for both read and write functions. Internally generated and
regulated voltages are provided for the program and erase operations.

The A29L400A is entirely software command set compatible with the JEDEC single-power-supply Flash standard.
Commands are written to the command register using standard microprocessor write timings. Register contents
serve as input to an internal state-machine that controls the erase and programming circuitry. Write cycles also internally latch addresses and data needed for the programming and erase operations. Reading data out of the device is similar to reading from other Flash or EPROM devices.

Device programming occurs by writing the proper program command sequence. This initiates the Embedded Program
algorithm - an internal algorithm that automatically times the program pulse widths and verifies proper program margin.

Device erasure occurs by executing the proper erase command sequence. This initiates the Embedded Erase algorithm - an internal algorithm that automatically preprograms the array (if it is not already programmed)
before executing the erase operation. During erase, the device automatically times the erase pulse widths and
verifies proper erase margin. The Unlock Bypass mode facilitates faster programming times by requiring only two
write cycles to program data instead of four.

The host system can detect whether a program or erase operation is complete by observing the RY / BY pin, or by
reading the I/O7 (Data Polling) and I/O6 (toggle) status bits. After a program or erase cycle has been completed, the
device is ready to read array data or accept another command.

The sector erase architecture allows memory sectors to be erased and reprogrammed without affecting the data contents of other sectors. The A29L400A is fully erased when shipped from the factory.

The hardware sector protection feature disables operations for both program and erase in any combination of the
sectors of memory. This can be achieved via programming equipment.

The Erase Suspend/Erase Resume feature enables the user to put erase on hold for any period of time to read data from, or program data to, any other sector that is not selected for erasure. True background erase can thus be achieved.

The hardware RESET pin terminates any operation in progress and resets the internal state machine to reading
array data. The RESET pin may be tied to the system reset circuitry. A system reset would thus also reset the device,
enabling the system microprocessor to read the boot-up firmware from the Flash memory.

The device offers two power-saving features. When addresses have been stable for a specified amount of time,
the device enters the automatic sleep mode. The system can also place the device into the standby mode. Power
consumption is greatly reduced in both these modes.