Operating instructions

After the load, we execute the RTS
in the tape loader routine. Since we did
not jump
to it as a subroutine for the
load of the last segment, all
it does is to
pull 0200
off the stack and uses this as
the location of the next instruction
to ex-
ecute.
Therefore by loading those initial
16
bytes in the first program described, we
cause the machine to load program 1
which began automatically to load in
turn programs
2, 3, and 4. Then it began
the execution
of our loaded segmented
program at location
0200.
The only cautionary note in using
this type of sequenced loading is to be
certain
that the load control segment is
located in the area
of memory which is
overlayed last by the final program seg-
ment to
be loaded (04 in this case).
Otherwise you will erase the loader
before the entire group of segments
is
brought in.
The
16-byte setup program you will
note is fully relocatable, and could even-
tually
be linked as a part of your monitor
routines. However to make
it more
general in
that case, the instructions
Figure 1: The Bootstrap Program
(Load and
start Segment Loader)
now specified at 0208 could be, for ex-
ample, A5 EE, or reference any other
zero page location so that the
10 byte
could
be preloaded there by the user and
retrieved by this routine for use later.
This also assumes
that the user has
committed this routine to
ROM.
This sequenced loading technique
has other uses as well, but that is
another subject and may be the subject
of a future article.
0200
20 86
88
JSR ACCESS
;UNPROTECT
SYSTEM RAM
0203
A9
00
LDA #$00
:STACK LO
BYTE
OF
0205
48
PHA
;PROGRAM
01 START
ADDR.
0206
A9 02
LDA
,11$02
,STACK
HI
BYTE
OF
0208
48
PHA
; PROGRA
~
01
START
ADOR.
0209
AO
00
LDY 1$ 00
:T APE
MODE ( 80
IF HI
spo. )
0208
A9
01
LOA
.1ISOl
:PROGRAM
10 SE ARCHED
0200
4C
78 8e
JMP
LOADT
:LDAD
PHDGRAM
01.
Figure 2: The Segment Loader Program:
Loads segments 02, 03. ]4 then starts execution at location 0200.
0200
20 ~6 fB
JSR ACCESS ; UtoolPROTECT
SYS TEM R.AM
0203
A9 00
LDA
#$00
;STACK
LO BYTE
OF
PRCGRJlM
0205
48
PHA ;START
ADDRESS
0206 A9
02
LDA
#$02
;STACK
t .. n
BYTE
OF
PRCGRJM
0208
48 PHA
;S TART
ADDRESS
0209
AO 00
LDY
#$00
;KIM
MODE: (80
FOR
HI SPC. J
0208 A9
02
LOA
#S02
;PROGRA1lI
10 02
020D
20
78 EC JSR
LOADT
:JSR TO TAPE
LOAD SUEROUT I
NE
0210
AD 00 LOY #$ 00 ,TAPE
MCDE
0212
A9
03 LOA
#$03
;IO
03
0214 20 78
BC JSR LOADT
;
JSR TO
TAPE
LOAD
0217
AO 00
LOY
#SOO
;T APE MODE
0219 A9
04 LOA
#$04
aD
04
021B
4C 78 8e
JMP LOADT
:T APE L CAD
*JUMP *
t
BEG INS
; PROGRA~ AT
0200 'III HEN
LOAD
DONE.
r
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