14

µPD75P218

4.3

PROM READ PROCEDURE

The PROM contents can be read in the verify mode by using the following procedure: (see the following

figure)

(1) Connect unused pins to VSS. Set the X1 pin low.

(2) Supply 5 volts to the VDD and VPP pins.

(3) Wait for 10

µs.

(4) Select the clear program memory address mode.

(5) Supply 6 volts to the VDD and 12.5 volts to the VPP pins.

(6) Select the program inhibit mode.

(7) Select the verify mode. Apply four pulses to the X1 pin. Every four clock pulses will output the data stored

in one address.

(8) Select the program inhibit mode.

(9) Select the clear program memory address mode.

(10) Return the VDD and VPP pins back to + 5 volts.

(11) Turn off the power.

Fig. 4-2 PROM Read Timing

VPP

VPP

VDD

VDD

VDD+1

VDD

X1

MD0

(P30)

P40 - P43

P50 - P53

MD1

(P31)

MD2

(P32)

MD3

(P33)

Output data

Output data

“L”