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MOTOROLA M68040 USER’S MANUAL 5- 13
Table 5-6. Processor Status Encoding
Hex PST3 PST2 PST1 PST0 Internal Status
00000User, Start/Continue Current Instruction
10001User, End Current Instruction
20010User, Branch Not Taken/End Current Instruction
30011User, Branch Taken/End Current Instruction
40100User, Table Search
50101Halted State (Double Bus Fault)
60110Low-Power Stop Mode (Supervisor Instruction)*
70111Reserved
81000Supervisor, Start/Continue Current Instruction
91001Supervisor, End Current Instruction
A1010Supervisor, Branch Not Taken/End Current Instruction
B1011Supervisor, Branch Taken/End Current Instruction
C1100Supervisor, Table Search
D1101Stopped State (Supervisor Instruction)
E1110RTE Executing
F1111Exception 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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