Z8F021ASH020SC datasheet(32/276 Pages) ZILOG

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PS022815-0206

Address Space

Z8 Encore! XP® 4K Series

Product Specification

Address Space

Overview

The eZ8 CPU can access three distinct address spaces:

• The Register File contains addresses for the general-purpose registers and the eZ8 CPU,

peripheral, and general-purpose I/O port control registers.

• The Program Memory contains addresses for all memory locations having executable

code and/or data.

• The Data Memory contains addresses for all memory locations that contain data only.

These three address spaces are covered briefly in the following subsections. For more

detailed information regarding the eZ8 CPU and its address space, refer to the eZ8 CPU

User Manual available for download at www.zilog.com.

The Register File address space in the Z8 Encore!® MCU is 4KB (4096 bytes). The Regis-

ter File is composed of two sections: control registers and general-purpose registers. When

instructions are executed, registers defined as sources are read, and registers defined as

destinations are written. The architecture of the eZ8 CPU allows all general-purpose regis-

ters to function as accumulators, address pointers, index registers, stack areas, or scratch

pad memory.

The upper 256 bytes of the 4KB Register File address space are reserved for control of the

eZ8 CPU, the on-chip peripherals, and the I/O ports. These registers are located at

addresses from F00H to FFFH. Some of the addresses within the 256B control register sec-

tion are reserved (unavailable). Reading from a reserved Register File address returns an

undefined value. Writing to reserved Register File addresses is not recommended and can

produce unpredictable results.

The on-chip RAM always begins at address 000H in the Register File address space. The

Z8 Encore! XP® 4K Series devices contain 256B to 1KB of on-chip RAM. Reading from

produces no effect.

Z8F021ASH020SC Datasheet(PDF) 32 Page - Zilog, Inc.