13

µPD75P218

4.2

PROM WRITE/VERIFY PROCEDURE

PROMs can be written at high speed 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 zero 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) Write data in the 1 ms write mode.

(8) Select the program inhibit mode.

(9) Select the verify mode. If the data is correct, proceed to step (10). If not, repeat steps (7), (8) and (9).

(10) Perform one additional write (duration of 1 ms

× number of writes at (7) to (9)).

(11) Select the program inhibit mode.

(12) Apply four pulses to the X1 pin to increment the program memory address by one.

(13) Repeat steps (7) to (12) until the end address is reached.

(14) Select the zero clear program memory address mode.

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

(16) Turn off the power.

Fig. 4-1 PROM Write Timing

VPP

Write

Verify

Additional write

Address

increment

X repetition

VPP

VDD

VDD

VDD+1

VDD

X1

MD0

(P30)

P40 - P43

P50 - P53

MD1

(P31)

MD2

(P32)

MD3

(P33)

Input data

Output

data

Input data

X: number of writes performed at (7) to (9)