Digital Photo Keychain User Manual

INSTRUCTION DESCRIPTIONS
A - 266 INSTRUCTION SET DETAILS MOTOROLA
Operation: Assembler Syntax:
SSH ➞ PC; SSL ➞ SR; SP–1 ➞ SP RTI
Description: Pull the program counter (PC) and the status register (SR) from the system
stack. The previous program counter and status register are lost.
Restrictions: Due to pipelining in the program controller and the fact that the RTI
instruction accesses certain program controller registers, the RTI instruction must not be
immediately preceded by any of the following instructions:
Immediately before RTI MOVEC to SR, SSH, SSL, or SP
MOVEM to SR, SSH, SSL, or SP
MOVEP to SR, SSH, SSL, or SP
MOVEC from SSH
MOVEM from SSH
MOVEP from SSH
ANDI MR or ANDI CCR
ORI MR or ORI CCR
An RTI instruction cannot be the last instruction in a DO loop (at LA).
An RTI instruction cannot be repeated using the REP instruction.
Example:
:
RTI ;pull PC and SR from system stack
:
Explanation of Example: The RTI instruction pulls the 16-bit program counter (PC) and
the 16-bit status register (SR) from the system stack and updates the system stack
pointer (SP).
RTI Return from Interrupt RTI