1541←TRI.DOC
FILE INFORMATION
FILENAME(S): 1541←TRI.DOC
FILE TYPE(S): PRG
FILE SIZE: 11.4K
FIRST SEEN: 2025-12-02 02:01:44
APPEARS ON: 1 disk(s)
FILE HASH
21c04f81897837824a35bb82f7955ea434d0c1615cb34c8b4b84cc6b2ed7cf71
FOUND ON DISKS (1 DISKS)
| DISK TITLE | FILENAME | FILE TYPE | COLLECTION | TRACK | SECTOR | ACTIONS |
|---|---|---|---|---|---|---|
| DISK | 1541←TRI.DOC | PRG | marcus | 16 | 0 | DOWNLOAD FILE |
FILE CONTENT & ANALYSIS
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00002C70: 61 79 20 62 65 0A 74 68 65 20 62 65 73 74 20 77 |ay be.the best w|
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00002D70: 2E 6E 7A 20 20 20 20 56 69 63 74 6F 72 69 61 20 |.nz Victoria |
00002D80: 55 6E 69 76 65 72 73 69 74 79 20 6F 66 20 57 65 |University of We|
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00002DA0: 61 6C 61 6E 64 2E 0A 0A |aland... |
FROM: STUCE@CSV.WARWICK.AC.UK (PETER WEI
GHILL).NEWSGROUPS: COMP.SYS.CBM.SUBJECT:
1541 DISK DRIVE COMMANDS..DATE: 25 SEP
1993 19:20:47 +0100.ORGANIZATION: COMMOD
ORE 64 SERVICES, UNIVERSITY OF WARWICK,
UK...TWO RARELY USED 1541 DISK DRIVE FUN
CTIONS...1. THE UTILITY LOADER '&' COMMA
ND...INTRODUCTION .. A LITTLE KN
OWN AND LITTLE USED COMMAND ON THE 1541
DISK DRIVE IS THE."&" COMMAND. THIS IS P
ROBABLY DUE TO THE FACT THAT THERE IS NO
MENTION OF IT.IN THE "1541 DISK DRIVE U
SERS GUIDE". MANY OTHER BOOKS ABOUT THE
DISK DRIVE.ALSO FAIL TO MENTION IT. AS T
O A USE FOR THE COMMAND, I HAVE NOT FOUN
D ONE.YET. PERHAPS SOMEONE COULD THINK O
F ONE. I WOULD EXPECT THAT THE 1570/1571
.AND 1581 DRIVE WILL ALSO CONTAIN THE "&
" COMMAND AS WELL, SINCE THEY ARE.BASED
ON THE 1541...UTILITY LOADER ("&" COMMA
ND).. THE UTILITY LOADER IS THE COMM
AND WHICH WILL LOAD A USR FILE FROM.DISK
INTO DISK DRIVE MEMORY WHERE IT WILL TH
EN EXECUTE. THE FORMAT FOR.THE COMMAND I
S AS FOLLOWS:.OPEN15,8,15:PRINT#15,"&FIL
ENAME":CLOSE15..USR FILES.. A USER F
ILE HAS TO FOLLOW CERTAIN GUIDLINES. IT
IS LIMITED TO JUST.ONE SECTOR AND THIS S
ECTOR IS CONSTRUCTED AS BELOW;..BYTE.0
START ADDRESS LOW ORDER.1 STAR
T ADDRESS HIGH ORDER.2 NUMBER OF BY
TES IN PROGRAM.3+ PROGRAM CODE BYTES
.LAST CHECKSUM.. THIS MEANS THAT T
HE MAXIMUM SIZE OF PROGRAM CODE IS 251 B
YTES. THE.CHECKSUM BYTE IS CALCULATED BY
ADDING ALL THE VALUES OF THE BYTES, STA
RTING.AT THE LOW ORDER START ADDRESS (BY
TE 0), WHILE ADDING YOU SUBTRACT 255 FRO
M.THE TOTAL EVERY TIME IT EXCEEDS 255. T
HUS THE CHECKSUM BYTE CAN RANGE FROM.1-2
55.. ONE FINAL CONSTRAINT IS THAT TH
E FILENAME MUST BEGIN WITH AN "&"..
BELOW IS A PROGRAM WHICH WILL MAKE IT EA
SIER FOR YOU TO CREATE A USR.FILE IN THE
REQUIRED FORMAT, SO THAT IT CAN BE EXEC
UTED BY THE UTILITY.LOADER COMMAND. THE
PROGRAM AUTOMATICALLY CALCULATES THE LEN
GTH OF THE CODE.AND ALSO THE CHECKSUM AT
THE END. ALL YOU NEED TO DO IS ADD YOUR
OWN CODE.TO THE DATA STATEMENTS BETWEEN
210 AND 300 AND SPECIFY A FILENAME IN L
INE 10...10 OPEN2,8,2,"0:&FILENAME,U,W"
.20 READLO,HI:C=LO+HI:IFC>255THENC=C-25
5.30 PRINT#2,CHR$(LO)CHR$(HI);.40 T$="
".50 READD:IFD=-1THEN100.60 C=C+D:IFC>
255THENC=C-255.70 T$=T$+CHR$(D).80 GOT
O50.100 L=LEN(T$).110 C=C+L:IFC>255THENC
=C-255.120 PRINT#2,CHR$(L)T$CHR$(C);.130
CLOSE2.140 END.170 :.200 DATA 0,5 :REM
LO/HI START ADDRESS.210 : REM PR
OGRAM CODE.220 DATA 173,0,28,41,16,201,1
6,208,11.230 DATA 169,247,45,0,28,141,0,
28,76.240 DATA 0,5,32,24,193,76,0,5.300
DATA -1 :REM PROGRAM DATA FINISHED..
THE EXAMPLE CODE IN THE PROGRAM IS NOT
THAT USEFUL, IT IS JUST THERE.TO SHOW H
OW THE UTILITY LOADER WORKS. IT JUST SWI
TCHES THE DRIVES LIGHT ON.AND OFF DEPEND
ING ON IF THE WRITE PROTECT SENSOR IS CO
VERED OR NOT.. IF YOU CAN THINK OF S
OMETHING WHICH COULD BE DONE WITH THE UT
ILITY.LOADER THEN I WOULD LOVE TO HEAR O
F IT...ERRORS THAT CAN OCCUR..39, 'FILE
NOT FOUND'. THIS OCCURS IF THE FI
LE YOU SPECIFIED USING THE UTILITY LOADE
R. COMMAND DOES NOT EXIST OR IS N
OT A USR FILE...50, 'RECORD NOT PRESENT'
. THE CHECKSUM CALCULATED BY TH
E DISK DRIVE AND THE CHECKSUM AT THE.
END OF THE FILE DIFFER...51, 'OVERF
LOW IN RECORD'. EITHER: 1. THE EN
D OF THE FILE WAS REACHED BEFORE THE CHE
CKSUM. BYTE WAS READ..
OR 2. THE FILE CONTAINS EXT
RA BYTES OF DATA AFTER THE CHECKSUM.
BYTE.. CHECK THE L
ENGTH BYTE IN THE USR FILE (POSITION 3,
AFTER LO/HI.)....2. CHECKING THAT A FILE
IS ON THE DISK...INTRODUCTION.. IF
YOU WROTE A PROGRAM WHICH NEEDED TO CHEC
K THAT A PARTICULAR FILE.EXISTED ON A DI
SK THEN YOU WOULD PROBABLY OPEN THE FILE
FOR A READ, THEN.CHECK THE ERROR CHANNE
L FOR 62, FILE NOT FOUND...THUS:.10 OPEN
15,8,15.20 OPEN2,8,2,"FILENAME,P,R".30 I
NPUT#15,E,E$.40 IFE>0THENPRINTE$:GOTO60.
50 PRINT"FILE EXISTS".60 CLOSE2:CLOSE15.
. ANOTHER WAY TO CHECK IF A FILE EXI
STS IS TO TRY TO RENAME IT AS ITSELF...T
HUS:.10 OPEN15,8,15,"R:FILENAME=FILENAME
".20 INPUT#15,E,E$.30 CLOSE15.40 PRINTE$
.. IF THE FILE EXISTS THEN THE ERROR
CREATED IS 63, FILE EXISTS,.OTHERWISE I
T IS 62, FILE NOT FOUND. JUDGE FOR YOURS
ELF WHICH WORKS BETTER....WRITTEN, SEPTE
MBER 93, BY PETER WEIGHILL. EMAIL: STU
CE@WARWICK.CSV.AC.UK....FROM: NICHOLAS.C
ULL@COMP.VUW.AC.NZ (NICHOLAS CULL).NEWSG
ROUPS: COMP.SYS.CBM.SUBJECT: RE: 1541 DI
SK DRIVE COMMANDS..DATE: 30 SEP 1993 00:
00:20 GMT.ORGANIZATION: DEPT. OF COMP. S
CI., VICTORIA UNI. OF WELLINGTON, NEW ZE
ALAND..ORIGINATOR: NCULL@COMP.VUW.AC.NZ.
..IN ARTICLE <28225V$1S3@TANSY.CSV.WARWI
CK.AC.UK>, STUCE@CSV.WARWICK.AC.UK. (PET
ER WEIGHILL) WRITES:.|> .|> 1. THE UTILI
TY LOADER '&' COMMAND........|> A U
SER FILE HAS TO FOLLOW CERTAIN GUIDLINES
. IT IS LIMITED TO JUST.
^^^
^^^^^^^^^^^^^^^^^^.|> ONE SECTOR AND THI
S SECTOR IS CONSTRUCTED AS BELOW;. ^^^
^^^^^^^..THIS IS INCORRECT. THE USER FIL
E MAY BE MORE THAN ONE SECTOR LONG, ALTH
OUGH THE.MAXIMUM SIZE OF THE PROGRAM COD
E IS LIMITED TO 256 BYTES. TO OBTAIN THI
S, BYTE.2 (THE NUMBER OF BYTES IN PROGRA
M) SHOULD BE SET TO 0. A FORMULA FOR THI
S.WOULD BE..(NB AND 255)..WHERE NB IS TH
E NUMBER OF BYTES. REMEMBER THAT THE CHE
CKSUM HAS TO BE UPDATED.IN A SIMILAR WAY
TOO, EG.. C = C+(NB AND 255): IF C>255
THEN C=C-255..THE NUMBER OF BYTES IN A B
LOCK-EXECUTE COMMAND IS LIMITED TO A SIN
GLE SECTOR,.WHICH IS 256 BYTES, ALTHOUGH
THESE CAN BE ALL DATA BYTES. MAYBE YOU
WERE.CONFUSING THE TWO COMMANDS?..|> .|>
BYTE.|> 0 START ADDRESS LOW ORDER
.|> 1 START ADDRESS HIGH ORDER.|> 2
NUMBER OF BYTES IN PROGRAM.|> 3+
PROGRAM CODE BYTES.|> LAST CHECKSUM
.|> ..IN FACT THERE CAN BE MORE THAN ONE
BLOCK OF THIS CONSTRUCTION PER FILE. TO
DO.THIS, SIMPLY REPEAT THE CONSTRUCTION
. FOR EXAMPLE, IF YOU WANTED TO HAVE A.P
ROGRAM WHICH SAT IN DRIVE LOCATIONS $030
0 TO $0400, AND $0480 TO $0500, THE.CONS
TRUCTION WOULD BE AS FOLLOWS:..BYTE.0
LOW BYTE START ADDRESS OF FIRS
T BLOCK (0).1 HIGH BYTE STAR
T ADDRESS OF FIRST BLOCK (3).2
NUMBER OF BYTES IN THIS BLOCK (0)
[= 256 AND 255].3 - 259 PROGRA
M CODE FOR FIRST BLOCK (DATA GOES IN HER
E...).260 CHECKSUM FOR FIRST B
LOCK (WHATEVER THIS MAY BE)..261
LOW BYTE START ADDRESS OF SECOND BLOC
K (128).262 HIGH BYTE START AD
DRESS OF SECOND BLOCK (4).263
NUMBER OF BYTES IN THIS BLOCK (128).264
- 392 PROGRAM CODE FOR SECOND BLOCK
(SECOND LOT OF DATA HERE).393
CHECKSUM FOR SECOND BLOCK (WHATEVER)..OK
AY, SO THIS MAY NOT BE THE BEST DESCRIPT
ION IN THE WORLD, BUT HOPEFULLY YOU.GET
THE GENERAL IDEA. THERE MAY BE AS MANY B
LOCKS OF THIS TYPE AS YOU NEED,.AND THEY
CAN ALL BE ANY SIZE FROM 1 TO 256 BYTES
LONG. ONCE THE FILE HAS BEEN.COMPLETELY
LOADED INTO THE DRIVE, EXECUTION STARTS
FROM THE START ADDRESS OF.THE FIRST BLOC
K BE BE TRANSFERRED...|> THE TOTAL EVERY
TIME IT EXCEEDS 255. THUS THE CHECKSUM
BYTE CAN RANGE FROM.
^^^^^^^^^^^^^^^^^^^^
^^^^^^^^^^^^^^^^^.|> 1-255.. ^^^^^^..T
HE CHECKSUM COULD BE 0 IF ALL THE DATA B
YTES WERE 0 :-)..SERIOUSLY THOUGH, THE P
OINT OF HAVING THE CHECKSUM CALCULATED I
N THIS WAY IS TO.MAKE USE OF THE CARRY B
IT IN MACHINE CODE ADDITION IF A CARRY I
S GENERATED. THE.POINT CAN BE MADE MORE
CLEARLY IN THE FOLLOWING CODE FRAGMENT:.
. [ACCUMULATOR HOLDS CURRENT DATA
BYTE]. CLC ;CLEAR CARRY B
IT FOR FIRST ADD. ADC $87 ;ADD
BYTE TO CURRENT CHECKSUM. ADC #$
00 ;ADD CARRY BIT TO CHECKSUM.
STA $87 ;SAVE CHECKSUM TO MEMORY..IF
THE SUM OF THE ACCUMULATOR AND THE CONTE
NTS OF LOCATION $87 IS GREATER THAN.#$FF
THEN THE CARRY FLAG WILL BE SET, IN ORD
ER TO DO MULTI-BYTE ADDITION.CORRECTLY.
INSTEAD OF ADDING THIS TO A SECOND BYTE
HOWEVER, IT IS ADDED TO THE.SAME BYTE WH
ICH GENERATED THE CARRY. THIS CAUSES THE
VALUE IN THE ACCUMULATOR.TO BE INCREMEN
TED BY 1 - THE SAME AS IF #$FF HAD BEEN
SUBTRACTED FROM IT...IF THE SUM IS OF TH
E ACCUMULATOR AND THE CONTENTS OF LOCATI
ON $87 IS LESS THAN.OR EQUAL TO #$FF, TH
EN NO CARRY IS GENERATED AND NO FURTHER
ADDITION OR.SUBTRACTIONIS NEEDED...|>
BELOW IS A PROGRAM WHICH WILL MAKE IT
EASIER FOR YOU TO CREATE A USR.|> FILE
IN THE REQUIRED FORMAT, SO THAT IT CAN B
E EXECUTED BY THE UTILITY.|> LOADER COMM
AND.....HERE IS A NEW VERSION THE THE PR
OGRAM, MODIFIED TO HANDLE MULTIPLE DATA
BLOCKS,.AND A MAXIMUM PROGRAM SIZE OF 25
6 BYTES PER BLOCK:.. 10 OPEN2,8,
2,"0:&FILENAME,U,W". 20 READNB.
30 READLO,HI,LN:C=LO+HI:C=C+(C>2
55)*255. 40 C=C+(LNAND255):C=C+(
C>255)*255. 50 PRINT#2,CHR$(LO);
CHR$(HI);CHR$(LNAND255);. 60 REA
DD:PRINT#2,CHR$(D);. 70 C=C+D:C=
C+(C>255)*255. 80 LN=LN-1:IFLN>0
THEN60. 90 PRINT#2,CHR$(C);.
100 NB=NB-1:IFNB>0THEN30. 110
CLOSE2. 120 END. 190 :.
200 DATA2 :REM NUMBER OF DAT
A BLOCKS. 210 DATA128,3 :REM LO
/HI START ADDRESS OF FIRST BLOCK.
220 DATA6 :REM LENGTH OF FIRST BL
OCK. 230 : REM PROGRAM
CODE. 240 DATA32,71,198,76,0,3.
300 DATA0,3 :REM LO/HI START
ADDRESS OF SECOND BLOCK. 310 DATA
26 :REM LENGTH OF SECOND BLOCK.
320 : REM REST OF PROGRAM
CODE. 330 DATA173,0,28,41,16,201
,16,208,11. 340 DATA169,247,45,0,
28,141,0,28,76. 350 DATA0,3,32,24
,193,76,0,3..THE EXAMPLE CODE HERE IS JU
ST A MINOR EXTENSION TO THE ORIGINAL COD
E. IT.RE-INITIALIZES THE DRIVE BEFORE JU
MPING TO THE ORIGINAL CODE. THIS IS JUST
TO.DEMONSTRATE THAT BOTH PARTS OF THE C
ODE ARE BEING LOADED AND EXECUTED.CORREC
TLY. ..|> ERRORS THAT CAN OCCUR.|> .|> 5
1, 'OVERFLOW IN RECORD'.|> EITHE
R: 1. THE END OF THE FILE WAS REACHED BE
FORE THE CHECKSUM.|>
BYTE WAS READ..|> OR 2. THE
FILE CONTAINS EXTRA BYTES OF DATA AFTER
THE CHECKSUM. ^^^^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^^^^^^^^^^^.|> BYTE.
. ^^^^^.|>
CHECK THE LENGTH BYTE IN THE USR FILE (P
OSITION 3, AFTER LO/HI.)..THE SECOND CON
DITION IS NOT QUITE ACCURATE. IF END-OF-
FILE IS REACHED BEFORE.THE DRIVE EXPECTS
TO READ THE CHECKSUM, THEN THIS ERROR W
ILL OCCUR. IF EXTRA.BYTES APPEAR AFTER T
HE CHECKSUM, THE DRIVE ASSUMES THESE TO
BE THE START OF A.NEW BLOCK OF DATA AND
WILL TRY TO INTERPRET THESE AS ADDRESS B
YTES, LENGTH.BYTE, DATA BYTES ETC AS ABO
VE. WHEN END-OF-FILE APPEARS, THE DRIVE
WILL REPORT.THIS ERROR, SINCE IT IS EXPE
CTING ANOTHER BLOCK OF DATA TO APPEAR AN
D CANNOT.COMPLETE THE TRANSFER OF THIS I
NTO MEMORY. HENCE THE DEFINITION OF THIS
ERROR.SHOULD BE:.. THE END OF TH
E FILE WAS ENCOUNTERED UNEXPECTEDLY. MAY
INDICATE AN. INCORRECT LENGTH BY
TE, OR ADDITIONAL DATA WRITTEN AFTER THE
END OF THE. LAST DATA BLOCK...NO
TE THE SEMICOLON AT THE END OF LINE 90 O
F THE PROGRAM. IF THIS WERE OMITTED,.A C
ARRIAGE RETURN BYTE WOULD BE SENT BY THE
COMPUTER AFTER THE CHECKSUM BYTE.AND MA
Y BE THE CAUSE OF THIS MESSAGE...ONE CAU
TION SHOULD BE ADDED AT THIS POINT. ALTH
OUGH DATA MAY BE TRANSFERRED TO.ANY ADDR
ESS IN THE RAM OF THE DRIVE, IT SHOULD B
E REMEMBERED THAT PART OF THE.MEMORY WIL
L BE ALLOCATED TO BUFFERING THE FILE AS
IT COMES OFF THE DISK. THUS.IT MAY BE PO
SSIBLE TO OVERWRITE INCOMING DATA BEING
BUFFERED IN MEMORY BEFORE.IT CAN BE TRAN
SFERRED CORRECTLY TO ITS NEW LOCATION. E
XPERIMENTATION MAY BE.THE BEST WAY OF DE
TERMINING WHICH AREAS ARE "SAFE" AND WHI
CH ONES HAVE.PROBLEMS. I FOUND THAT THE
FILE SEEMED TO BE BUFFERED IN LOCATIONS
$0600 TO.$0700, BUT THIS WOULD DEPEND ON
HOW MAY FILES YOU HAD OPEN, ETC...NICK.
..----. EMAIL: NCULL@COMP.VUW.AC.NZ V
ICTORIA UNIVERSITY OF WELLINGTON, NEW ZE
ALAND...
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