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8- 22 M68040 USER’S MANUAL MOTOROLA
EXIT
OTHER FORMATS
FORMAT CODE = $1
(THROWAWAY 
FRAME)
SR TEMP 
SP SP + 6
PC (SP) +
SP SP + 6
SR TEMP
TEMP (SP)+
READ FORMAT WORD
ENTRY
INVALID FORMAT 
WORD
OTHERWISE
OTHERWISE
FORMAT CODE = $0 
(4-WORD FRAME)
OTHERWISE
TAKE FORMAT
ERROR EXCEPTION
Figure 8-6. Flowchart of RTE Instruction for Throwaway Four-Word Frame
8.4.3 Six-Word Stack Frame (Format $2)
If a six-word throwaway stack frame is on the active stack and an RTE instruction is
encountered, the processor restores the SR and PC values from the stack, increments the
active supervisor stack pointer by $C, and resumes normal instruction execution.
Stack Frames Exception Types Stacked PC Points To
STATUS REGISTER
PROGRAM COUNTER
0 0 1 0 VECTOR OFFSET
015
SP
+$02
+$06
SIX-WORD STACK FRAME–FORMAT $2
ADDRESS
+$08
CHK, CHK2, TRAPcc,
FTRAPcc, TRAPV, Trace,
or Zero Divide
Unimplemented Floating-
Point Instruction
Address Error
Next Instruction: address is
the address of the
instruction that caused the
exception.
Next Instruction: address is
the calculated <ea> for the
floating-point instruction.
Instruction that caused the
address error, address is
the reference address – 1.
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