Z8F6421PM020SC Datasheet, PDF (37/299 Pages) Zilog, Inc. – High Performance 8-Bit Microcontrollers Z8 Encore-R 64K Series

Z8 Encore!^® 64K Series
Product Specification
17
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 hold 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 64K Series is 4KB (4096 bytes). The Register File
is composed of two sections—control registers and general-purpose registers. When
instructions are executed, registers are read from when defined as sources and written to
when defined as destinations. The architecture of the eZ8 CPU allows all general-purpose
registers 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 256-byte control register
section are reserved (unavailable). Reading from an reserved Register File addresses
returns an undefined value. Writing to reserved Register File addresses is not recom-
mended and can produce unpredictable results.
The on-chip RAM always begins at address 000H in the Register File address space. The
64K Series provide 2KB to 4KB of on-chip RAM depending upon the device. Reading
from Register File addresses outside the available RAM addresses (and not within the con-
trol register address space) returns an undefined value. Writing to these Register File
addresses produces no effect. Refer to the Part Selection Guide on page 2 to determine
the amount of RAM available for the specific 64K Series device.
PS019915-1005
Address Space