MC68LC040RC25A Datasheet, PDF (235/442 Pages) Freescale Semiconductor, Inc – M68040 Users Manual

Freescale Semiconductor, Inc.
ENTRY
TEMP (SP)+
READ FORMAT WORD
SR TEMP
SP SP + 6
INVALID FORMAT
WORD
TAKE FORMAT
ERROR EXCEPTION
OTHERWISE
OTHERWISE
FORMAT CODE = $1
(THROWAWAY
FRAME)
FORMAT CODE = $0
OTHERWISE (4-WORD FRAME)
OTHER FORMATS
PC (SP) +
SP SP + 6
SR TEMP
EXIT
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
15
0
SP
STATUS REGISTER
+$02
PROGRAM COUNTER
+$06
0010
+$08
VECTOR OFFSET
ADDRESS
SIX-WORD STACK FRAME–FORMAT $2
Exception Types
• CHK, CHK2, TRAPcc,
FTRAPcc, TRAPV, Trace,
or Zero Divide
• Unimplemented Floating -
Point Instruction
• Address Error
Stacked PC Points To
• 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.
8-22
M68040 USER’S MANUAL
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