MOTOROLA
M68040 USER’S MANUAL
5- 13
Table 5-6. Processor Status Encoding
Hex
PST3
PST2
PST1
PST0
Internal Status
00000
User, Start/Continue Current Instruction
10001
User, End Current Instruction
20010
User, Branch Not Taken/End Current Instruction
30011
User, Branch Taken/End Current Instruction
40100
User, Table Search
50101
Halted State (Double Bus Fault)
60110
Low-Power Stop Mode (Supervisor Instruction)*
70111
Reserved
81000
Supervisor, Start/Continue Current Instruction
91001
Supervisor, End Current Instruction
A
1010
Supervisor, Branch Not Taken/End Current Instruction
B
1011
Supervisor, Branch Taken/End Current Instruction
C
1100
Supervisor, Table Search
D
1101
Stopped State (Supervisor Instruction)
E
1110
RTE Executing
F
1111
Exception Stacking
NOTE: *MC68040V and MC68EC040V only.
When a ‘branch taken/end current instruction’ is indicated, it means that a change of
instruction flow is pending. Along with the following instructions, an exception stacking
(encoding F) sequence is ended with the ‘supervisor, branch taken/end current instruction’
encoding as though it were a virtual JMP instruction. This includes all the possible
exceptions listed in the processor’s vector table. Instructions that cause a ‘branch
taken/end current instruction’ encoding when they are executed are as follows:
ANDI to SR
DBcc (Taken)
MOVE to SR
RTD
Bcc (Taken)
FBcc (Taken)
MOVE USP
RTE
BRA
FDBcc (Always)
MOVEC
RTR
BSR
FMOVEM Rc,MRn
MOVES
RTS
CAS
FMOVEM FPm,MRn
NOP
STOP
CAS2
FSAVE
ORI to SR
TAS
CINV
JMP
PFLUSH
CPUSH
JSR
PTEST
The Bcc (not taken) and DBcc (not taken) are the only instructions that cause a ‘branch
not taken/end current instruction’ encoding. Note that the FBcc (not taken) is not included
in this category. The FBcc (not taken) instruction ends with an ‘end current instruction’
encoding. All other instructions and conditions end with the ‘end current instruction’
encoding. For instance, if the processor is running back-to-back single clock instructions,
the encoding ‘end current instruction’ remains asserted for as many clock cycles as
instructions.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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