Zilog Z8F0130 - Manual (Page 302)

Using the Macro Assembler UM013037-1212
278
Zilog Developer Studio II – Z8 Encore!
User Manual
Address Spaces and Segments
You access the memory regions of the Z8 Encore! microcontroller by using segment direc-
tives. A segment is a contiguous set of memory locations. All segments are attached to
exactly one memory space. The Z8 Encore! Assembler has predefined spaces and seg-
ments. The following sections describe address spaces and segments:
•
Allocating Processor Memory – see page 278
•
Address Spaces – see page 278
•
Segments – see page 279
•
Assigning Memory at Link Time – see page 281
Allocating Processor Memory
All memory locations, whether data or code, must be defined within a segment. There are
two types of segments:
•
Absolute segments
An absolute segment is any segment with a fixed origin. The origin of a segment can
be defined with the ORG directive. All data and code in an absolute segment are
located at the specified physical memory address.
•
Relocatable segments
A relocatable segment is a segment without a specified origin. At link time, linker
commands are used to specify where relocatable segments are to be located within
their space. Relocatable segments can be assigned to different physical memory loca-
tions without reassembling.
Address Spaces
The memory regions for the Z8 Encore! microprocessor are represented by the address
spaces listed in the
Linker: Address Spaces Page section on page 103. Briefly, the main
address spaces are the ROM space (used for program storage and some constant data) and
the data spaces RData and EData. Both RData and EData are used to store nonconstant
data; RData is 8-bit addressable memory with a maximum range of
00H-FFH , and EData
is 12-bit addressable memory with a maximum range of 100H-EFFH . Some CPUs also
have specialized Nonvolatile Data Storage (NVDS) and Program RAM (PRAM) spaces,
which are described more fully in the
Linker: Address Spaces Page section on page 103.
Code and data are allocated to these spaces by using segments attached to the space.