EPROM/OTPROM (PROM)

EPROM/OTPROM (PROM) Programming

9.3.1 Program Register

The program register (PROG) shown in Figure 9-3 is used for PROM programming.

LAT — Latch Enable Bit

This bit is both readable and writable.

1 = Enables PROM data and address bus latches for programming on the next byte write cycle

0 = Latch disabled. PROM data and address buses are unlatched for normal CPU operations.

PGM — Program Bit

If LAT is cleared, PGM cannot be set.

1 = Enables VPP power to the PROM for programming

0 = VPP is disabled.

Bits 1 and 3− 7 — Not used; always read 0

EPROM/OTPROM (PROM)

9.3.2 Preprogramming Steps

Before programming the PROM using an MC68HC05PGMR PCB in standalone mode, the user should ensure that:

•A jumper is installed on pins 1 and 2 of mode select header J1.

•An EPROM is programmed with the necessary user code.

•The erasure window (if any) of the device to be programmed is covered.

•VDD of +5 Vdc is available on the board.

•VPP is available on the board.

NOTE: If the VPP level at the MCU exceeds +16 Vdc, then the MC68HC705C8A

MCU device will suffer permanent damage.

Once those conditions are met, the user should take these steps before beginning programming:

1.Remove the VPP power source.

2.Set switch 1 in the OFF position (removes VDD).

3.Place the programmed EPROM in socket U1.

4.Insert the erased PROM MCU device to be programmed in the proper socket:

–MC68HC705C8S or MC68HC705C8P in socket U2 (40-pin dual in-line package (DIP)) or

–MC68HC705C8FN in socket U3 (44-pin plastic leaded chip carrier (PLCC)) with the device notch at the upper right corner of the socket.

5.Set switch S2 in the RESET position.

NOTE: No PROM MCU should be inserted in or removed from its board socket

(U2 or U3) while VPP (P1, slot 5) or VDD (switch 1) is active on the board.