Z8 Encore! XP
®
4K Series
Product Specification
13
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.
Register File
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
Register File addresses outside the available RAM addresses (and not within the control
register address space) returns an undefined value. Writing to these Register File addresses
produces no effect.
PS022815-0206
Address Space
ZILOG [ ZILOG, INC. ]
