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CHAPTER 3 CPU ARCHITECTURE
User’s Manual U12697EJ3V0UM
The registers used in other cases always become the same registers regardless of the contents of the RSS bit.
For registers A, X, B, C, AX, and BC in NEC assembler RA78K4, instruction code is generated for any register
described by name or for registers set by an RSS quasi directive in the assembler.
When the RSS bit is set or reset, always specify an RSS quasi directive immediately before (or immediately after)
that instruction (see the following examples).
<Program examples>
•
When RSS = 0
RSS 0
; RSS quasi directive
CLR1 PSWL. 5
MOV B, A
; This description corresponds to “MOV R3, R1”.
•
When RSS = 1
RSS 1
; RSS quasi directive
SET1 PSWL. 5
MOV B, A
; This description corresponds to “MOV R7, R5”.
(2) Generation of instruction code in the RA78K4
•
In the RA78K4, when an instruction with the same function as an instruction that directly specifies A or AX
in the operand column in the operation list of the instruction is used, the instruction code that directly describes
A or AX in the operand column is given priority and generated.
Example
The MOV A,r instruction where r is B has the same function as the MOV r, r’ instruction where r
is A and r’ is B. In addition, they have the same (MOV A,B) description in the assembler source
program. In this case, RA78K4 generates code that corresponds to the MOV A, r instruction.
