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CPIM-86 Bootstrap and Adaptation Procedures
The standard LDBIOS has been field-altered for the APC hardware using the same
entry points described in Chapter 5 for BIOS modification. The organization of
LOADER is shown in Figure 8-1.
GD#l]OV III I I IIII I II
CS DS ES SS OOOOH:
JMP 1200H
I
(LDCPM)
I
JMPF CPM
0400H:
( LDBDOS)
1200H:
JMP INIT
.......
JMP SETIOB
INIT: .. JMP 0003H
(LDBIOS)
1700H:
Figure 8-1 LOADER Organization
Byte offsets from the base registers are shown at the left of the diagram. GD#1 is the
Group Descriptor for the LOADER code group described above, followed imme-
diately by a "0" group terminator. The entire LOADER program is read by the
BOOT ROM, excluding the header record, starting at byte location 04000H as given
by the A-Field. Upon completion of the read, the BOOT ROM passes control to
location 04000H where the LOADER program begins execution. The JMP 1200H
instruction at the base of LDCPM transfers control to the beginning of the LDBIOS
where control then transfers to the INIT subroutine. The subroutine starting at
INIT performs device initialization, prints a sign-on message, and transfers back to
the LDCPM program at byte offset 0003H. The LDCPM module opens the
CPM.SYS file, loads the CP/M-86 system into memory and transfers control to
CP/M-86 through the JMPF CPM instruction at the end of LDCPM execution,
thus completing the cold start sequence.
8-3
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