Motorola DSP56000 Manual page 576

Immediately before JSCLR from SSH or SSL,xxxx
Immediately before JSSET from SSH or SSL,xxxx
Also, the instruction MOVEC SSH,SSH is illegal.
A.9.6 R, N, and M Register Restrictions
Due to pipelining, if an address register Rn is the destination of a MOVE-type instruction
except MOVEP (MOVE, MOVEC, MOVEM, LUA, Tcc), the new contents will not be
available for use as an address pointer until the second following instruction cycle.
Likewise, if an offset register Nn or a modifier register Mn is the destination of a MOVE-
type instruction except MOVEP, the new contents will not be available for use in address
calculations until the second following instruction cycle.
However, if the processor is in the No Update addressing mode (where Mn and Nn are
ignored) and register Mn or Nn is the destination of a MOVE instruction, the next instruc-
tion may use the corresponding Rn register as an address pointer. Also, if the processor
is in the Postincrement by 1, Postdecrement by 1, or Predecrement by 1 addressing
mode (where Nn is ignored), a MOVE to Nn may be immediately followed by an instruc-
tion that uses Rn as an address pointer.
Note: This restriction also applies to the situation in which the last instruction in a DO
loop changes an address register using a move-type instruction and the first instruction
at the top of the DO loop uses that same address register. The top instruction becomes
the following instruction because of the loop construct. The DSP assembler will gener-
ate a warning if this condition is detected.
A.9.7 Fast Interrupt Routines
The following instructions may not be used in a fast interrupt routine:
In a fast interrupt routine
A - 310
INSTRUCTION SEQUENCE RESTRICTIONS
DO
ENDDO
RTI
RTS
MOVEC to LA, LC, SSH, SSL, SP, or SR
MOVEM to LA, LC, SSH, SSL, SP, or SR
MOVEP to LA, LC, SSH, SSL, SP, or SR
MOVEC from SSH
INSTRUCTION SET DETAILS
BCHG to SP
BCLR to SP
BSET to SP
BCHG to SP
BCLR to SP
BSET to SP
MOVEM from SSH
MOVEP from SSH
ORI MR or ORI CCR
ANDI MR or ANDI CCR
STOP
SWI
WAIT
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