AT89C1051

4-9

Chip Erase: The entire PEROM array (1K byte) and the

two Lock Bits are erased electrically by using the proper

combination of control signals and by holding P3.2 low for

10 ms. The code array is written with all “1”s in the Chip

Erase operation and must be executed before any non-

blank memory byte can be re-programmed.

Reading the Signature Bytes: The signature bytes are

read by the same procedure as a normal verification of

locations 000H, 001H, and 002H, except that P3.5 and

P3.7 must be pulled to a logic low. The values returned are

as follows.

(000H) = 1EH indicates manufactured by Atmel

(001H) = 11H indicates 89C1051

Programming Interface

Every code byte in the Flash array can be written and the

entire array can be erased by using the appropriate combi-

nation of control signals. The write operation cycle is self-

timed and once initiated, will automatically time itself to

completion.

Figure 3. Programming the Flash Memory

Figure 4. Verifying the Flash Memory

P3.1

P3.3

P3.5

P3.2

RDY/BSY

PROG

SEE FLASH

PROGRAMMING

MODES TABLE

TO INCREMENT

ADDRESS COUNTER

P1

5V

P3.4

PGM

DATA

V/ V

I H

PP

P3.7

RST

XTAL1

GND

V

CC

AT89C1051

P3.3

P3.5

P3.2

P1

5V

P3.4

PGM

DATA

V

I H

V

I H

P3.7

RST

XTAL1

GND

V

CC

AT89C1051

SEE FLASH

PROGRAMMING

MODES TABLE