ST20CX datasheet(5/212 Pages) STMICROELECTRONICS

5 / 212 page

5/212

Introduction

This manual provides a summary and reference to the ST20 instruction set for C2 and

C4 cores. The instructions are listed in alphabetical order, one to a page. Descriptions

are presented in a standard format with the instruction mnemonic and full name of the

instruction at the top of the page, followed by these categories of information:

• Code: the instruction code;

• Description: a brief summary of the purpose and behavior of the instruction;

• Definition: a more complete description of the instruction, using the notation

described below in section 1.7;

• Error signals: a list of errors and other signals which can occur;

• Comments: a list of other important features of the instruction;

• See also: for some instructions, a cross reference is provided to other instruc-

tions with a related function.

These categories are explained in more detail below, using the

add instruction as an

example.

1.1

Instruction name

The header at the top of each page shows the instruction mnemonic and, on the right,

the full name of the instruction. For primary instructions the mnemonic is followed by

‘n’ to indicate the operand to the instruction; the same notation is used in the

description to show how the operand is used.

1.2

Code

For secondar y instructions the instruction ‘operation code’ is shown as the memory

code — the actual bytes, including any prefixes, which are stored in memory. The

value is given as a sequence of bytes in hexadecimal, decoded left to right. The codes

are stored in memory in ‘little-endian’ format — with the first byte at the lowest

address.

For primary instructions the code stored in memory is determined partly by the value

of the operand to the instruction. In this case the op-code is shown as ‘Function

x’

where

x is the function code in the last byte of the instruction. For example, adc (add

constant) is shown as ‘Function 8’.

Example

The entry for the

add instruction is:

Code:F5

ST20CX Datasheet(PDF) 5 Page - STMicroelectronics