Writing and verifying prom (program memory) – NEC PD75P308 User Manual

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PD75P308

Pin Name

Function

Applies voltage when program memory is written/verified (normally, at V

potential)

These pins input clock that updates address when program memory is written/verified. To X2 pin,

input signal 180º out of phase in respect to signal to X1 pin.

MD0-MD3

These pins select operation mode when program memory is written/verified.

P40-P43 (Lower 4)

P50-P53 (Upper 4)

Power supply voltage application pin.

Apply 5V

5% to this pin during normal operation and 6V when program memory is written/verified.

3. WRITING AND VERIFYING PROM (PROGRAM MEMORY)

The program memory of the

PD75P308 is a PROM of 8064 x 8 bits. To write data to or verify the contents

of this PROM, the pins listed in the table below are used. Note that no address input pins are provided

because the address is updated by the clock input through the X1 pin.

These pins input/output 8-bit data when program memory is written/verified.

X1, X2

Note 1: Always cover the erasure window of the

PD75P308K with a light-opaque film except when the

contents of the program memory are erased.

2: The one-time PROM model

PD75P308GF is not equipped with a window and therefore, the

contents of the program memory of this model cannot be erased by exposing it to ultraviolet rays.

3.1 OPERATION MODES FOR WRITING/VERIFYING PROGRAM MEMORY

When +6V is applied to the V

pin of the

PD75P308 with +12.5V applied to the V

pin, the

PD75P308

is set in the program memory write/verify mode. In this mode, the following operation modes can be set

by using the MD0-MD3 pins. At this time, pull down the levels of all the other pins to V

Operating Mode Specification

MD0

MD1

MD2

MD3

+6 V

+12.5 V

Operating Mode

Program memory address 0 clear mode

Write mode

Verify mode

Program inhibit mode

x: L or H