W49F102

Publication Release Date: October 2000

- 3 -

Revision A3

FUNCTIONAL DESCRIPTION

Read Mode

The read operation of the W49F102 is controlled by

CE

and

OE, both of which have to be low for

the host to obtain data from the outputs.

CE

is used for device selection. When

CE

is high, the

chip is de-selected and only standby power will be consumed.

OE

is the output control and is used

to gate data from the output pins. The data bus is in high impedance state when either

CE

or

OE

is high. Refer to the timing waveforms for further details.

Boot Block Operation

There is one 8K-word boot block in this device, which can be used to store boot code. It is located in

the first 8K words of the memory with the address range from 0000 hex to 1FFF hex.

See Command Codes for Boot Block Lockout Enable for the specific code. Once this feature is set the

data for the designated block cannot be erased or programmed (programming lockout); other memory

locations can be changed by the regular programming method. Once the boot block programming

lockout feature is activated, the chip erase function will only affect the main memory.

In order to detect whether the boot block feature is set on the 8K-words block, users can perform

software command sequence: enter the product identification mode (see Command Codes for

Identification/Boot Block Lockout Detection for specific code), and then read from address "0002 hex".

If the output data is "FF hex," the boot block programming lockout feature is activated; if the output

data is "FE hex," the lockout feature is inactivated and the block can be erased/programmed.

To return to normal operation, perform a three-byte command sequence (or an alternate single-word

command) to exit the identification mode. For the specific code, see Command Codes for

Identification/Boot Block Lockout Detection.

Chip Erase Operation

The chip-erase mode can be initiated by a six-word command sequence. After the command loading

cycle, the device enters the internal chip erase mode, which is automatically timed and will be

completed in a fast 100 mS (typical). The host system is not required to provide any control or timing

during this operation. If the boot block programming lockout is activated, only the data in the main

memory will be erased to FF(hex), and the data in the boot block will not be erased (remains same as

before the chip erase operation). The entire memory array (main memory and boot block) will be

erased to FF(hex). by the chip erase operation if the boot block programming lockout feature is not

activated. The device will automatically return to normal read mode after the erase operation

completed. Data polling and/or Toggle Bits can be used to detect end of erase cycle.

Main Memory Erase Operation

The main memory erase mode can be initiated by a six-word command sequence. After the command

loading cycle, the device enters the internal main-memory erase mode, which is automatically timed

and will be completed in a fast 100 mS (typical). The host system is not required to provide any control

or timing during this operation. The device will automatically return to normal read mode after the erase

operation completed. Data polling and/or Toggle Bits can be used to detect end of erase cycle.