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The AS29F040 is a 4-megabit, 5-volt-only Flash memory device organized as 512K bytes of 8 bits each. For flexible erase an
program capability, the 4 megabits of data is divided into eight 64K-byte sectors. The ×8 data appears on DQ0–DQ7. The
AS29F040 is offered in JEDEC standard 32-pin TSOP and 32-pin PLCC packages. This device is designed to be programmed an
erased in-system with a single 5.0V VCC supply. The device can also be reprogrammed in standard EPROM programmers.
The AS29F040 offers access times of 55/ 70/ 90/ 120/ 150 ns, allowing 0-wait state operation of high-speed microprocessors. To
eliminate bus contention the device has separate chip enable (CE), write enable (WE), and output enable (OE) controls
The AS29F040 is fully compatible with the JEDEC single power supply Flash standard. Write commands to the command register
use standard microprocessor write timings. An internal state machine uses register contents to control the erase and programming
circuitry. Write cycles also internally latch addresses and data needed for the programming and erase operations. Read data
operates from the device in the same manner as other Flash or EPROM devices. The program command sequence is used to invoke
the automated on-chip programming algorithm that automatically times the program pulse widths and verifies proper cell margin.
The erase command sequence is used to invoke the automated on-chip erase algorithm that preprograms the sector if it is not
already programmed before executing the erase operation, times the erase pulse widths, and verifies proper cell margin.
Sector erase architecture allows specified sectors of memory to be erased and reprogrammed without altering data in other sectors .
A sector typically erases and verifies within 1.0 seconds. Hardware sector protection disables both program and erase operations i n
any or all combinations of the eight sectors. The device provides true background erase with Erase Suspend, which puts erase
operations on hold to either read data from or program data to a sector that is not being erased. The chip erase command will
automatically erase all unprotected sectors.
A factory shipped AS29F040 is fully erased (all bits = 1). The programming operation sets bits to 0. Data is programmed into the
array one byte at a time in any sequence and across sector boundaries. A sector must be erased to change bits from 0 to 1. Erase
returns all bytes in a sector to the erased state (all bits = 1). Each sector is erased individually with no effect on other sectors.
The device features single 5.0V power supply operation for read, write, and erase functions. Internally generated and regulate
voltages are provided for the program and erase operations. A low VCC detector automatically inhibits write operations during
power transtitions. DATA polling of DQ7 or toggle bit (DQ6) may be used to detect end-of-program or erase operations. The
device automatically resets to read mode after program and/ or erase operations are completed.
The AS29F040 resists accidental erasure or spurious programming signals resulting from power transitions. Control register
architecture permits the alteration of memory contents only after successful completion of specific command sequences. During
power up, the device is set to read mode with all program and/ or erase commands disabled when VCC is less than VLKO (lockout
voltage). The command registers are not affected by noise pulses of less than 5 ns on OE, CE, or WE. CE and WE must be logical
zero and OE a logical one to initiate write commands.
The AS29F040 uses Fowler-Nordheim tunnelling to electrically erase all bits within a sector simultaneously. Bytes are programme
one at a time using the EPROM programming mechanism of hot electron injection.
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