Preliminary W49F020

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can be used to detect end of program cycle.

Hardware Data Protection

The integrity of the data stored in the W49F020 is also hardware protected in the following ways:

(1) Noise/Glitch Protection: A WE pulse with less than 15 nS in duration will not initiate a write cycle.

2.5V typical.

(3) Write Inhibit Mode: Forcing OE low, CE high, or WE high will inhibit the write operation. This

prevents inadvertent writes during power-up or power-down periods.

5 mS before any write (erase/program) operation.

The W49F020 features a data polling function which used to indicate the end of a program or erase

last word loaded will receive the complement of the true data. Once the program or erase cycle is

become logical "1" or true data when the erase cycle has been completed.

In addition to data polling, the W49F020 provides another method for determining the end of a program

alternating 0's and 1's. When the program or erase cycle is completed, this toggling between 0's and 1's

will stop. The device is then ready for the next operation.

Product Identification

The product ID operation outputs the manufacturer code and device code. Programming equipment

automatically matches the device with its proper erase and programming algorithms.

The manufacturer and device codes can be accessed by software or hardware operation. In software

access mode, a three-word (or JEDEC 3-word) command sequence can be used to access the product

ID. A read from address 0000H outputs the manufacturer code DA(hex); and a read from address

0001H outputs the device code 8C(hex) for W49F020. The product ID operation can be terminated by a

three-word command sequence or an alternated one-word command sequence (see Command

Definition table).

In the hardware access mode, access to the product ID will be activated by forcing CE and OE low,

WE

high, and raising A9 to 12 volts.