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MB90420/5 (A) SERIES F
21.2.2 Example of Correction Processing
After resetting, the MCU reads the contents of the EEPROM. If the byte count of the patch program is not
'0', the body of the patch program is read from the EEPROM and written to the RAM. Then the MCU sets the
program address either on PADR0 or on PADR1 and enables the operation. First address of the program
written in the RAM is stored into the RAM defined for each address detect register. In this case the INT9
service routine look for this user-defined address to jump to the patch program.
n Reset sequence
Read the 00
YES
0000
Read the address
0001
H
PADR0 • i M CU • j
Read the patch program
0010
H
000400
Enable compare
MOV PACSR, #02
Normal program execution
2
MC-16LX FAMILY 16-BIT MICROCONTROLLERS HARDWARE MANUAL
Reset
2
of E
PROM
H
2
(E
PROM) = 0
H
NO
2
to 0003
(E
PROM)
H
• « M OV
2
to 0090
(E
PROM)
H
• « M OV
to 000480
(MCU)
H
H
H
NO
PC = PADR0
YES
INT9
Fig. 21.4 ROM Correction Processing Flow
To patch program
Patch program execution
000400
End of patch program
21-8
INT9
JMP 000400
H
to 000480
H
H
JMP FF0050h
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