VIC-1541

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

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

[edit] Features

VIC-1541

VIC-1541c

1541-II

The successor of the VIC-1540, which can only be used with the VIC-20, can be used with the C64 and with some newer Commodore computers like C128/D/DCR, C16/116 and Plus/4. On 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.

On the back side of the case are two interfaces for serial data cables, the power switch and power connector. On the VIC-1541-II are two DIP-switches to change the device number (default 8). Depending on what model the current supply was, this happened with a rubber connector or a power-supply.

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

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

PRG program files (maximum filesize approximately 200 blocks)
SEQ sequential files (only usable with computer applications; max. filesize 168.656 Bytes)
USR user-files (special format of a sequential file)
REL relative files (only usable 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 the < char is printed after the file format, the file cannot be overwritten. It is write-protected by software.
If the * char is printed 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 is 144

The data transfer rate is about 300 Bytes/s, but can be higher by using a fast loader (up to about 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; type numbers:

         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 (3.8×7.8×14.7 inches)
Weight: 5 kg (11 lb)
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) e.g. to detect disk change: 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 (COPY): OPEN 1,8,15,"C:NewFile=OldFile": CLOSE 1; The command string might be maximal 40 chars in lenght!
Concatenate files (COMBINE): OPEN 1,8,15,"C:NewFile=1.OldFile,2.OldFile,...": CLOSE 1; The command string might be maximal 40 chars in length!
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 and status variable ST.

[edit] Hints

Activate VIC-20 mode for VIC1541 (slightly faster, incompatible with C64): OPEN 15,8,15,"UI-":CLOSE 15
Activate C64 mode for VIC1541: 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

In some models, 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" on the board of the disk drive.

[edit] Content of the test-/demo diskette

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 Main Program)
11  COPY/ALL          PRG (Copy Program)
9   PRINTER TEST      PRG (Printer Test)
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-/demo diskette can change slightly depending on the year of construction or modell.