Table 3-1 Implicit Stack Activity - Motorola DSP56600 Manual

Program Control
The Hardware Stack
3-4
The current stack location is pointed by the SP register. A single
stack location can store two words, referred to as occupying the
"high" and "low" halves of the stack location. The current stack
locations pointed by SP (top of stack) are named SSH and SSL,
respectively. A single "push" or "pop" activity can access the SSH
and SSL concurrently. Stack activities are triggered implicitly at
execution of specialized instruction or fulfillment of certain
conditions. These activities are summarized in Table 3-1.
Note: The table only summarizes the effect of those instructions on
the stack. Some instructions update other registers as well.
For complete information on an instruction, refer to
Appendix A in the DSP56300 and DSP56600 Family
Manuals .
Activity
JSR, BSR
jump to JScc, BScc (condition true)
subroutine JSCLR, BSCLR (condition true)
JSSET, BSSET (condition true)
return from
RTS
subroutine
return from
RTI
long interrupt
move to SSH MOVEC <source>,SSH
move from SSH MOVEC SSH,<destination>
DO
DOR
enter DO loop
DO FOREVER
DOR FOREVER
(LF bit set and FV bit clear
exit DO loop at and fetched address = LA
last address and LC = 0).
ENDDO
Optimizing DSP56300/DSP56600 Applications

Table 3-1 Implicit Stack Activity

Triggered by Instruction or
Condition
Implicit Stack
Actions Taken
SP: = SP + 1;
SSH: = PC; SSL: = SR.
PC: = SSH
SP: = SP - 1
PC: = SSH; SR: = SSL
SP: = SP – 1
SP: = SP + 1
SSH: = <source>
<destination>: = SSH
SP: = SP – 1
SP: = SP + 1
SSH: = LA, SSL: = LC
SP: = SP + 1
SSH: = PC, SSL: = SR
SR: = SSL
SP: = SP – 1
LA: = SSH, LC: = SSL
SP: = SP – 1
MOTOROLA