INSTRUCTION DESCRIPTIONS
A - 148 INSTRUCTION SET DETAILS MOTOROLA
Operation: Assembler Syntax:
ea➞d LUA ea,D
Description: Load the updated address into the destination address register D. The
source address register and the update mode used to compute the updated address are
specified by the effective address (ea). Note that the source address register speci-
fied in the effective address is not updated. All update addressing modes may be
used.
Note: This instruction is considered to be a move-type instruction. Due to instruction
pipelining, if an AGU register (Mn, Nn, or Rn) is directly changed with this instruction, the
new contents may not be available for use until the second following instruction. See the
restrictions discussed in A.9.6 - R, N, and M Register Restrictions on page A-310.
Example: :
LUA (R0)+N0,R1 ;update R1 using (R0)+N0
:
Explanation of Example: Prior to execution, the 16-bit address register R0 contains the
value $0003, the 16-bit address register N0 contains the value $0005, and the 16-bit
address register R1 contains the value $0004. The execution of the LUA (R0)+N0,R1
instruction adds the contents of the R0 register to the contents of the N0 register and
stores the resulting updated address in the R1 address register. Normally N0 would be
added to R0 and deposited in R0. However, for an LUA instruction, the contents of both
the R0 and N0 address registers are not affected.
LUA Load Updated Address LUA
Before Execution After Execution
R0 R0
N0 N0
R1 R1
$0004 $0008
$0005
$0003
$0005
$0003
M0 M0
$FFFF $FFFF