Zilog Z16F2810 Manuel d'utilisateur télécharger pdf (Page 19)

UM018809-0611 Architectural Overview

ZNEO

CPU Core

User Manual

Fetch Unit

The Fetch Unit’s primary function is to fetch opcodes and operand words (including

immediate data) from memory. The Fetch Unit also fetches interrupt vectors. The Fetch

Unit is pipelined and operates semi-independently from the execution unit. This Unit per-

forms a partial decoding of the opcode to determine the number of bytes to fetch for the

operation.

The Fetch Unit operation sequence functions as follows:

1. Fetch the first 2-byte opcode word.

2. Determine number of remaining opcode and operand words (one or two).

3. Fetch the remaining opcode and operand words.

4. Present the opcode and operands to the Instruction State Machine.

A ZNEO CPU instruction is always 1, 2, or 3 words long, including operands, and must be

aligned on an even address.

Figure 1. ZNEO CPU Block Diagram

Fetch Unit

Instruction and

Operand Fetch

Instruction State Machine

Arithmetic Logic Unit (ALU)

32-bit ALU Registers, R0-R15

Bus Arbiter

Internal

Non-volatile

Memory

Internal

RAM

8/16

Internal I/O

8/16

External

Memory

Interface

Program

Counter

Control

Registers

Execution Unit

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 215 216

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Zilog Z16F2810 Manuel d'utilisateur Page 19