ST9 datasheet(33/146 Pages) STMICROELECTRONICS

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ST9 USER GUIDE

3.3.1 Overview

For a complete description of the instruction set, you should refer to the ST9 Programming

Manual. The aim here is to give you an introduction to the ST9 instruction set and highlight

some of its best features in terms of power and ease of programming.

Most instructions of the ST9 exist in both byte and word forms. That is, they can operate on ei-

ther 8 (byte) or 16-bits (word). The mnemonics of the word-instructions all end with a “w”, as

in the following examples:

The new powerful instructions added to the ST9 are the CALLS, RETS, JPS instructions for

far branching to change the program segment and the instructions used for C language appli-

cations, LINK, LINKU, UNLINK and UNLINKU. Moreover, all instructions have been optimized

compared to Previous ST9.

3.3.1.1 Load Instructions

Beside the classical load instructions found on most microprocessors, there are four special

load instructions for moving data between two locations in memory.

One instruction to move data from data segment to data segment; lddd. This instruction al-

lows you to post-increment the destination and the source index register at the same time. The

ld instruction needs two instructions to do this. An example for moving a block of data would

be:

rr0,#Source

rr2,#Destination

; initialisation of the pointers

r5,#Num_loop

; number of elements to move

loop:

r4,(rr0)+

; transfer of one byte

(rr2)+,r4

djnz

r5,loop

The two ld instructions are coded using 6 bytes and executed in 24 cycles.

The same program with the lddd instruction:

rr0,#Source

rr2,#Destination

; initialisation of the pointers

Load

Add

Subtract

Logical

and

Logical or

Compare

Push

Pop

add

sub

and

push

pop

ldw

addw

subw

andw

orw

cpw

pushw

popw

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