Z8F1680SH020SG Datasheet, PDF (44/412 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F1680 Series
Product Specification
19
Chapter 3. Address Space
The eZ8 CPU can access the following three distinct address spaces:
• The Register File contains addresses for general-purpose registers, eZ8 CPU, peripher-
als and GPIO 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 sections. For more details
about the eZ8 CPU and its address space, refer to the eZ8 CPU Core User Manual
(UM0128), available for download at www.zilog.com.
3.1.
Register File
The Register File address space in the Z8 Encore!^® MCU is 4 KB (4096 bytes). The
Register 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
registers to function as accumulators, address pointers, index registers, stack areas, or
scratch pad memory.
The upper 256 bytes of the 4 KB Register File address space are reserved for control of the
eZ8 CPU, on-chip peripherals and the input/output ports. These registers are located at
addresses F00H to FFFH. Some of the addresses within the 256 B control register sections
are reserved (that is, unavailable). Reading from a reserved Register File address returns
an undefined value. Zilog does not recommend writing to the reserved Register File
addresses because doing so can produce unpredictable results.
The on-chip Register RAM always begins at address 000H in the Register File address
space. The F1680 Series MCU contains 1 KB or 2 KB of on-chip Register 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.
In addition, the F1680 Series MCU contains 1 KB of on-chip Program RAM. Normally it
is used as Program RAM and is present in the Program Memory address space (see the
Program Memory section on page 20). However, it can also be used as additional Register
RAM present in the Register File address space 800H–BFFH (1 KB Program RAM, 2 KB
Register RAM), or 400H–7FFH (1 KB Program RAM, 1 KB Register RAM), if you do not
PS025015-1212
PRELIMINARY
Address Space