
CPU32+
MOTOROLA
MC68360 USER’S MANUAL
5-41
.
Figure 5-11. Reset Operation Flowchart
When the aborted bus cycle is an instruction prefetch, the processor will not initiate excep-
tion processing unless the prefetched information is used. For example, if a branch instruc-
tion flushes an aborted prefetch, that word is not accessed, and no exception occurs.
When the aborted bus cycle is a data access, the processor initiates exception processing
immediately, except in the case of released operand writes. Released write bus errors are
delayed until the next instruction boundary or until another operand access is attempted.
Exception processing for bus error exceptions follows the regular sequence, but context
preservation is more involved than for other exceptions because a bus exception can be ini-
ENTRY
FETCH VECTOR #0
1 S
0 T0,T1
$7 I2:IO
$0 VBR
FETCH VECTOR #1
BUS ERROR
OTHERWISE
(VECTOR #0) SP
BUS ERROR
PREFETCH 3 WORDS
BUS ERROR/
ADDRESS
ERROR
OTHERWISE BEGIN
INSTRUCTION
EXECUTION
EXIT
(DOUBLE BUS FAULT)
ASSERT HALT
EXIT
±
OTHERWISE
(VECTOR #1) PC