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SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER

and ON-SCREEN DISPLAY CONTROLLER

MITSUBISHI MICROCOMPUTERS

Rev. 1.0

M37281MAH–XXXSP,M37281MFH–XXXSP

M37281MKH–XXXSP,M37281EKSP

Fig.8.12.1 Sequence at Detecting Software Runaway Detection

8.12. SOFTWARE RUNAWAY DETECT FUNC-

TION

This microcomputer has a function to decode undefined instructions

to detect a software runaway.

When an undefined op-code is input to the CPU as an instruction

code during operation, the following processing is done.

➀ The CPU generates an undefined instruction decoding signal.

➁ The device is internally reset because of occurrence of the unde-

fined instruction decoding signal.

➂ As a result of internal reset, the same reset processing as in the

case of ordinary reset operation is done, and the program restarts

from the reset vector.

Note, however, that the software runaway detecting function cannot

be invalid.

ADH,

01,S–2

01,S–1

H PCL PS

: Undefined instruction decode

Undefined instruction decoding signal

occurs.Internal reset signal occurs.

SYNC

Address

Data

Reset sequence

01,S

FFFE

FFFF16

: Invalid

: Program counter

: Stack pointer

L, ADH

: Jump destination address of reset

1 2 ... 113 114 115 116 117 118 119 120 121 122 123 ... 158 159

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Renesas PCA7401 Manual de usuario Pagina 118