Nios® II Processor Reference Guide

ID 683836
Date 10/22/2020
Public
Document Table of Contents

8.1.1. I-Type

The defining characteristic of the I-type instruction word format is that it contains an immediate value embedded within the instruction word. I-type instructions words contain:
  • A 6-bit opcode field OP
  • Two 5-bit register fields A and B
  • A 16-bit immediate data field IMM16

In most cases, fields A and IMM16 specify the source operands, and field B specifies the destination register. IMM16 is considered signed except for logical operations and unsigned comparisons.

I-type instructions include arithmetic and logical operations such as addi and andi; branch operations; load and store operations; and cache management operations.

Table 87.  I-Type Instruction Format
Bit Fields
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
A B IMM16
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
IMM16 OP

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