Z8F042ASJ020EG2156 Datasheet, PDF (220/280 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F082A Series
Product Specification
205
Assembly Language Source Program Example
JP START
START:
LD R4, R7
LD 234H, #%01
; Everything after the semicolon is a comment.
; A label called ‘START’. The first instruction (JP START) in this
; example causes program execution to jump to the point within the
; program where the START label occurs.
; A Load (LD) instruction with two operands. The first operand,
; Working Register R4, is the destination. The second operand,
; Working Register R7, is the source. The contents of R7 is
; written into R4.
; Another Load (LD) instruction with two operands.
; The first operand, Extended Mode Register Address 234H,
; identifies the destination. The second operand, Immediate Data
; value 01H, is the source. The value 01H is written into the
; Register at address 234H.
Assembly Language Syntax
For proper instruction execution, eZ8 CPU assembly language syntax requires that the
operands be written as ‘destination, source’. After assembly, the object code usually has
the operands in the order ‘source, destination’, but ordering is opcode-dependent. The fol-
lowing instruction examples illustrate the format of some basic assembly instructions and
the resulting object code produced by the assembler. This binary format must be followed
if manual program coding is preferred or if you intend to implement your own assembler.
Example 1. If the contents of registers 43H and 08H are added and the result is stored in
43H, the assembly syntax and resulting object code is:
Table 116. Assembly Language Syntax Example 1
Assembly Language Code
Object Code
ADD 43H, 08H
04 08 43
(ADD dst, src)
(OPC src, dst)
Example 2. In general, when an instruction format requires an 8-bit register address, that
address can specify any register location in the range 0–255 or, using Escaped Mode
Addressing, a Working Register R0–R15. If the contents of Register 43H and Working
Register R8 are added and the result is stored in 43H, the assembly syntax and resulting
object code is:
Table 117. Assembly Language Syntax Example 2
Assembly Language Code
Object Code
ADD 43H, R8
04 E8 43
(ADD dst, src)
(OPC src, dst)
PS022828-0413
PRELIMINARY
Assembly Language Syntax