Panasonic MN101C77C, F77G user manual ROM Correction, Correction Sequence

Chapter 2 CPU Basics

2-7 ROM Correction

2-7-1 Overview

This LSI can correct and change max. 3 parts in a program on mask ROM with ROM correction function. The correct program is read from the external to the RAM space by using the external EEPROM or by using the serial transmission. This function is valid to the system with the external EEPROM.

2-7-2 Correction Sequence

Program is corrected as following steps.

(1)The instruction execution address is compared to the correction address.

(2)Program counter is branched indirectly to the RAM address (the head address of the correct pro- gram) stored to the RC vector table (RCnV(L), RCnV(H)), after matching the above addresses. This instruction needs 6 cycle.

(3)The corrected program at the RAM area is executed.

(4)Program counter is branched back to the program at ROM area.

label 1

label 2_

NG Instruction

When a match occurs, the program

counter branches indirectly to

the start address of the correct program.

the head address to be corrected

recover

RCnV(L)

RCnV(H)

Correct program

Development data from the external EEPROM

JMP label2_

internal ROM internal RAM

Figure 2-7-1 ROM Correction

II- 30 ROM Correction