Electronics America Personal Computer User Manual

PD75P308

3.3 PROGRAM MEMORY READ PROCEDURE

The contents of the program memory can be read in the following procedure.

(1) Ground the unused pins through pull-down resistors. The X1 pin must be low.

(2) Supply 5 V to the V

DD and VPP pins.

(3) Wait for 10 microseconds.

(4) Set program memory address 0 clear mode.

(5) Supply 6 V to the V

DD pin and 12.5 V to the VPP pin.

(6) Set program inhibit mode.

(7) Set verify mode. Data of each address is sequentially output each time a clock pulse is input to the

X1 pin four times.

(8) Set program inhibit mode.

(9) Set program memory address 0 clear mode.

(10) Change the voltages of V

DD and VPP pins to 5 V.

(11) Turn off the power supply.

Steps (2) to (9) are illustrated below.

VPP

VDD

VDD+1

VPP

VDD

Data output Data output

P40-P43

P50-P53

MD0

(P30)

MD1

(P31)

MD2

(P32)

MD3

(P33)