M37221M4H/M6H/M8H/MAH–XXXSP/FP M37221EASP/FP
8.12 SOFTWARE RUNAWAY DETECT FUNCTION
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.
➀ The device is internally reset due to the undefined instruction de-
coding signal.
➀ 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 disabled.
φ
SYNC
AD
AD
H
,
Address
Data
PC
?
01,S
01,S–1
01,S–2
FFFE16
FFFF16
L
?
PCH
PC
L
PS
AD
L
ADH
Reset sequence
Undefined instruction decoding signal
occurs.Internal reset signal occurs.
: Undefined instruction decode
?
: Invalid
: Program counter
: Stack pointer
PC
S
AD
L, ADH: Jump destination address of reset
Fig. 8.12.1 Sequence at Detecting Software Runaway Detection
Rev.1.00 Oct 01, 2002 page 74 of 110
REJ03B0134-0100Z
RENESAS [ RENESAS TECHNOLOGY CORP ]
