VIC-1541

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Short name for the Commodore-disk drive VIC-1541 (also VIC-1541, CBM-1541 or Commodore-1541; in Germany VC-1541), which is useable with 5,25"-disks. This disk drive has only one reading/writing head. It is connected over a data cable with the serial bus to the Commodore 64. In consequence of the long production time of the C64, the VC-1541 was produces with various cases, with internal or external power supplies, starting in 1983. Two newer models were introduced later, the VC-1541C (in 1986) and the VC-1541-II (in 1988).

1 Features
2 Technical Details
3 Disk Drive Commands
4 Hints
5 Content of the test-/demodisk
6 Links

[edit] Features

VC-1541

VC-1541c

1541-II

The successor of the VIC-1540, which can only be used at the VIC-20, can be used at the C64 and at some newer Commodore computers like C128/D/DCR, C16/116 and Plus/4. At the front of the case are 2 LEDs - a green for power control and a red for working status. When the red LED is flashing, an error occurred.

At the flipside of the case are 2 interfaces for serial data cable, the power-switcher and power-connector. At the VC-1541-II exist 2 DIP-switches to change the device number (optional 8). Depending on what modell the current supply was, this happend with a rubber connector or a power-supply.

One side of a 5,25"-disk has got in the VIC-1541 174,848 bytes, which are 683 blocks, but only 664 blocks are useable.

The disk drive VIC-1541 knows the following file formats:

PRG program files (max. filesize approx. 200 blocks)
SEQ sequential files (only useable with computer applications; max. filesize 168.656 Bytes)
USR user-files (special format of a sequential file)
REL relative files (only useable with computer applications; max. filesize 167.132 Bytes with max. 65.535 data sets)
DEL deleted files (with hints or manipulation of the directory this file type can be viewed)
If this char < stands after the file format, the file cannot be overwritten. It will be locked software-sided.
If this char * stands after the file format, the file isn't properly closed. The deleting of this file is done only through the dos-command VALIDATE !
Maximal number of files in a directory: 144

The data transfer rate is ~ 300 Bytes/s, but it will be higher by using a fast loader (up to ~ 10 KByte/s). The used version of Commodore-DOS is 2.6.

[edit] Technical Details

Chips: MOS 6502 (CPU) with ca. 1 MHz, 2x VIA 6522
RAM: 2 KByte (4x 2114)
ROM: 16 KByte; Typenr.:

         1541-1: 325302-01 (DOS V2.6 LoROM $C000-$DFFF), 
                 901229-XX (DOS V2.6 HiROM $E000-$FFFF)
         1541-C: 251968-01 (DOS V2.6 $C000-$FFFF)
         1541-2: 251968-03 (DOS V2.6 $C000-$FFFF)

Interfaces: Serial bus
Total capacity: 174,848 bytes per disk
Sequential files: 168,656 bytes per disk
Relative files: 167,132 bytes per disk, 65,535 records per file
Entries of a directory: 144 per disk
Sectors per track: 17 to 21
Tracks: 35
Blocks: 683 (664 blocks free)

Dimensions: 97*200*374 mm
Weight: 5 kg
Current supply: 100,120,220 or 240V with 50 or 60 Hz
Power input: 25W

[edit] Disk Drive Commands

The disk drive is controlled using a number of drive commands.

Format a disk (NEW): OPEN 1,8,15,"N:Diskname, ID": CLOSE 1; or: OPEN 1,8,15: PRINT#1,"N:Diskname, ID": CLOSE 1; The diskname has got max. 16 chars and the ID has got 2 chars.
Initialize drive (INITIALIZE): OPEN 1,8,15,"I":CLOSE 1
Validate a disk (VALIDATE): Does a check/rebuild of the disk's maintenance data structures (directory, block allocation map, etc.); OPEN 1,8,15,"V": CLOSE 1
Copy files together (COPY): OPEN 1,8,15,"C:NewFile=1.OldFile,2.OldFile,...": CLOSE 1; The charstring has got maximal 40 chars!
Rename a file (RENAME): OPEN 1,8,15,"R:New_Name=Old_Name":CLOSE 1
Delete a file (SCRATCH): OPEN 1,8,15,"S:filename": CLOSE 1; Wildcards such as * (matches any chars) or ? (matches one char) are supported.; For example: OPEN 1,8,15,"S:*":CLOSE 1 all files of a disk will be deleted.; With comma (,) more than one file can be deleted.
Overwrite a file (REPLACE): SAVE"@:filename",8 or
OPEN 1,8,15,"@:filename,S,W": CLOSE 1.; The REPLACE command is buggy - it may fail and you could lose all data of a disk. The better way is to first to use SCRATCH and after that the BASIC command SAVE.

These BASIC-commands can be used with the disk drive, too: CLOSE, GET#, INPUT#, LOAD, OPEN, PRINT#, SAVE and VERIFY.

[edit] Hints

Activate VC 20 mode for VC1541 (slightly faster, incompatible with C64): OPEN 15,8,15,"UI-":CLOSE 15
Activate C64 mode for VC1541: OPEN 15,8,15,"UI+":CLOSE 15

device number (8-15) can be changed temporarily by software with:
OPEN 15,8,15:PRINT#15,"M-W";CHR$(119);CHR$(0);CHR$(2);CHR$(device number+32)+CHR$(device numver+64):CLOSE 15

device number (8-11) can be changed permanently by hardware over DIP-switches ( 1-2 or A-B):

Device number	DIP-1/A	DIP-2/B
8	on	on
9	off	on
10	on	off
11	off	off
top: on - bottom: off

At some modells, that don't have any DIP-switches, the device number can be set by manipulating the terminal tag. The terminal tags are called "Device Jumpers" at the board of the diskdrive.

[edit] Content of the test-/demodisk

Test/Demo disk

Side 1:

13  HOW TO USE        PRG (engl. instruction 1.part)
5   HOW TO USE TWO    PRG (engl. instruction 2.part)
1   C-64 WEDGE        PRG (Utility-Starter C64)
4   VIC-20 WEDGE      PRG (Utility-Starter für VIC/VC20)
4   DOS 5.1           PRG (Utility-Mainprogram)
11  COPY/ALL          PRG (Copyprogram)
9   PRINTER TEST      PRG (Printertest)
4   DISK ADDR CHANGE  PRG (Change device number by software)
4   DIR               PRG (Easier using of Disk-Commands)
6   VIEW BAM          PRG (BAM-Viewer)
4   CHECK DISK        PRG (Diskcheck with VALIDATE)
14  DISPLAY T&S       PRG (Block-Viewer in Decimal or Hexadecimal)
9   PERFORMANCE TEST  PRG (Floppy-Check)
5   SEQUENTIAL FILE   PRG (Program example for SEQ-files)
13  RANDOM FILE       PRG (Program example for special DOS-Commands)
558 BLOCKS FREE

Remark: The content of the test-/demodisk can change a little bit depending on the year of construction or modell.