M37281EKSP Datasheet, PDF (117/172 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER and ON-SCREEN DISPLAY CONTROLLER

M37281MAH–XXXSP,M37281MFH–XXXSP,M37281MKH–XXXSP, M37281EKSP
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.
φ
SYNC
Address
PC
?
01,S
01,S–1 ^01,S–2 FFFE16 ^FFFF16
ADH,
ADL
Data
?
PCH
Undefined instruction decoding signal
occurs.Internal reset signal occurs.
PCL
PS
ADL
ADH
Reset sequence
: Undefined instruction decode
? : Invalid
PC : Program counter
S _{: Stack pointer}
ADL, ADH ^{: Jump destination address of reset}
Fig.8.12.1 Sequence at Detecting Software Runaway Detection
Rev.1.01 2003.07.16 page 117 of 170