Rom Correction; Overview; Correction Sequence - Panasonic F77G User Manual

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 NG Instruction
label 2_
internal ROM
II - 30
ROM Correction
When a match occurs, the program
counter branches indirectly to
the start address of the correct program.
the head address to be corrected
recover
Figure 2-7-1
RCnV(L)
RCnV(H)
Correct program
JMP label2_
internal RAM
ROM Correction
Development data
from the external EEPROM