Table of Contents
Advertisement
Command Setup and Execution Under CPIM-86
The Small Memory Model
The Small Model is assumed when the transient program contains both code and
data groups. (In ASM-86, all code is generated following a CSEG directive, while
data is defined following a DSEG directive. The origin of the data segment is
independent of the code segment.) In this model, register CS is set to the beginning
of the code group, registers DS and ES to the start of the data group, and registers
SS and SP to the CCP's stack area, as shown in Figure 2-2.
SS:
CCP
SS + SP:
CCP Stack
CS:
IP
=
OOOOH
code
DS ES:
base
page
DS+OI00H:
data
Figure 2-2 CP/M-86 Small Memory Model
The machine code begins at CS+OOOOH, the base page values begin at DS+OOOOH,
and the data area starts at DS+OI00H. The following ASM-86 example shows how
to code a Small Model transient program.
cseg
(code)
dseg
org
100h
(data)
end
2-5
Advertisement
Table of Contents
