dsp56800 Freescale Semiconductor, Inc, dsp56800 Datasheet - Page 378

• Manufacturer Part Number: dsp56800
• Description: 16-bit Digital Signal Controllers
• Manufacturer: Freescale Semiconductor, Inc

RTI
Operation:
X:(SP) → SR; SP-1→ SP
X:(SP) → PC; SP-1→ SP
Description: Return to normal execution at the end of an interrupt service routine. The return restores the status reg-
Example:
Explanation of Example:
Restrictions:
Condition Codes Affected:
Instruction Fields:
Timing:
Memory:
A-148
Operation
RTI
ister (SR) and program counter (PC) from the software stack. The previous PC is lost, and execution
resumes at the address that is indicated by the (restored) PC.
RTI
The RTI instruction pulls the 16-bit PC and the 16-bit SR from the stack and updates the system SP.
Program execution continues at $754C.
Due to pipelining in the program controller and the fact that the RTI instruction accesses certain pro-
gram controller registers, the RTI instruction must not be immediately preceded by any of the follow-
ing instructions:
An RTI instruction cannot be the last instruction in a DO loop (at the LA).
An RTI instruction cannot be repeated using the REP instruction.
10 + rx oscillator clock cycles
1 program word
Before Execution
X:$00FF
X:$0100
LF
15
SR
SP
14
*
MOVE(C) to the SP
Any bit-field instruction performed on the SR
All bits — Set according to the value pulled from the stack
13
*
Operands
12
754C
1300
0309
0100
*
MR
11
*
Return from Interrupt
DSP56800 Family Manual
10
*
I1
9
10
C
Assembler Syntax:
RTI
I0 SZ
8
W
1
7
Return from interrupt, restoring 16-bit PC and SR from
the stack
L
6
E
5
After Execution
X:$00FF
X:$0100
; pull the SR and PC registers
;
U
4
CCR
SR
SP
from the stack
N
3
Z
Comments
2
754C
00FE
1300
1300
V
1
Freescale Semiconductor
C
0
RTI