Radio Shack TRS-80 Owner's Manual page 133

f
!i
DISK
BASIC
L
il
5SOURCE ADDRESS
7D00 21003C 00230 ZAP LD
HL .VIDEO
7D03 3BBF
00240
LD
(HLS .WHITE
5
PUT OUT 1ST
BYTE
7D05 11013C
00250 LD
DE.MIDEO+1
^DESTINATION ADDRESS
7D08 01FFB3
00260 LD
BC .COUNT
I
NUMBER
OF
ITERATIONS
7D0B EDB0
00270
00280
;
LDIR iDO IT
TO IT!
! !
7D0D C9
00290
RET
!
RETURN
TO
BASIC
7D00
00300
END
ZAP
This routine
can be
POKEd
Into
ram
and accessed as
a
usr
routine. First
start
basic and
answer
the
MEMORY SIZE
question with
31999.
Then
ran
the
program.
100
'
PROGRAM: USR1
110
'
EXAMPLE OF
A
USER MACHINE LANGUAGE FUNCTION
115 '
DEPRESS
THE
'@'
KEY
WHILE NUMBERS ARE PRINTING TO
STOP
120
'
130 /
**#*#*
POKE
MACHINE PROGRAM INTO
MEMORY *******
140
'
150
DEFUSR1
=
&H7D00
160
FOR
X
=
32000
TO
32013 '7D00 HEX
EQUAL 32000 DECIMAL
170
READ
A
180
POKE
X. A
190
NEXT
X
192
'
194
'
******* CLEAR SCREEN
&
PRINT NUMBERS
1
THRU 100
*******
196
'
200 CLS
205 PRINT TAB(15)5
"WHITE-OUT USER ROUTINE"; PRINT
210 FOR
X
=
1
TO 100
220
PRINT
X!
225 A$ =
INKEY*:
IF
A$
=
"@"
THEN END
230 NEXT
X
240 '
250
'
******* JUMP
TO
WHITE-OUT SUBROUTINE *******
2G0 '
270
X
=
USR1
(0)
280 FOR
X
=
1
TO 1000:
NEXT
X
'DELAY LOOP
290 GOTO 200
300 '
310 /
###*#** DATA
IS
DECIMAL CODE FOR
HEX PROGRAM *******
320
'
330 DATA
33.0.60.54.191 .17.1 .60.1
.255.3.237.176.201
Run
the
program.
An
equivalent
basic white out routine takes a
long time
by comparison!
f^>~^-'7l7^Til
115