PET/CBM FAQ - PERIPHERALS AND INTERFACING

Tape Drives for the VIC, 64 and 128 work well on the PET. In fact you can hook up 2 tape drives on the PET (On non-original PETs the second connector is inside the case, on the left edge of the motherboard.) and can be accessed as device #2.

Besides the ones listed there have been several 3rd party drives made to work with the VIC-20 and Commodore 64, as well as standard cassette recorder “adapters” all of which also will work just as well on the PET.

• Modified Sanyo (possibly?) - First drives, power supply section cut out and modified for PET datasette cable/plug.
• C2N - Box look, black case.
• C2N - Box Look, cream colored case (w/counter).
• 1530 - Rounded low-profile, distance counter and 'save' indicator light. (not sown)

the PET uses the IEEE-488 interface to connect to disk drives. Back when they were new the drives themselves were pretty expensive (hard drives for microcomputers were a rarity then). The lower capacity drives (2031, 2020, 2040, 4040) are “read compatible” with the later Commodore 64 and VIC-20 1540 and 1541 drives and due to minor format variations it is unwise to try to write to a 1541 formatted disk with a PET drive and visa-versa, but for reading files from the other computer, it is a good method. The low density drives were designed initially for a single-density disk. Double density disks are OK to use. The IBM-PC High Density diskettes are not recommended as they would be unreliable on old drive electronics.

The 8050, 8250 and SFD-1001 use a “Quad Density” format (96 TPI) disk. These disks are not easy to find, as a substitute also use Double Density Diskettes, again the HD disks are problematic on the older hardware. Also you can use the 8250/SFD-1001 as if it were an 8050 drive (to read/write 8050 disks) by running a small BASIC program to reconfigure the drive settings. Unfortunately the 8050, 8250, SFD-1001 are all unable to read or write the low-capacity disk format used by the 2040,3040,4040,2031.

• 2020 Dual Floppy Drive - (first drive design, bugs will be present if old ROMs)
• 2040 Dual Floppy Drive - Updated ROMS, resembles a 1541 format and readable on 1541/71s
• 3040 Dual Floppy Drive - European 4040, like the 3000 series PETS?
• 4040 Dual Floppy Drive - Read compatible with 1541/1571s.
• 2031 Single Floppy Drive - Read compatible with 1541/1571s.
• 2031LP Single Floppy Drive - Same as above but in a grayish 1541 style case.
• 8050 Dual Floppy Drive - Single Sided/Quad Density format, 512k per disk side
• 8250 Dual Floppy Drive - Double Sided/Quad Density format, 1mb per disk
• 8250LP Dual Floppy Drive - Same as 8250 but with low profile grey plastic case colored like 1541 or 2031LP.
• SFD-1001 Single Floppy Drive - Same as 8250, but single drive unit in a 1541 style case.

• 8280 - 1 MB or 512k per Drive (little info on this one… called a monster for it's size and weight) reportedly IBM 8“format compatible the 8280 is one of the rarest of the Commodore IEEE-488 drives.

• 9060 - Five Megabyte Hard Disk Unit
• 9090 - Seven and a Half Megabyte Hard Disk Unit

• SD2PET Flash Drive - Provides a IEEE-488 drive emulation for the Commodore PET models, the SD2PET can store multiple disk images of software on a SD type memory card and emulate the disk drives so the PET can access them Much less size than traditional PET drivesand provides the ability to transfer files/disks from the internet using your PC.
• MSD-SD1 - Single Drive - 4040/1541 compatible offers both IEEE-488 and VIC/64 style interfaces
• MSD-SD2 - Dual Drive - 4040/1541 compatible offers both IEEE-488 and VIC/64 style interfaces
• Modified 1541
• Exatron Stringy Floppy - Kinda a cross between a tape drive (in connection and file storage) and a disk drive (in speed accessibility and capacity), more of a curiosity than in popular use.
• Computhink Disk Drive - This disk drive beat Commodore to the market (as the Commodore drive was delayed several times). Because of which the DOS commands and format of the disks are proprietary and not compatible with any Commodore disk drive.

Commodore Model IEEE-488 Printers

• 2022 - Tractor - Metal Case
• 2023 - Friction - Metal Case
• 4022 - Tractor Feed - Plastic Case (Epson MX-70 mechanism, pictured)
• 6400 - Wide Carriage Daisy Wheel Printer - TEC F-10 mechanism.
• 8023 - Tractor Feed - Wide carriage - Plastic case
• Some companies produced printers with IEEE-488 interface options (Epson was one, SWTP had a small recipt printer)
• Also available through some outfits were IEEE to Centronics/RS-232 Printer interfaces which would plug into the PET and offer you use of common centronics parallel or serial printers.

I know of only one company that produced a modem and IEEE-488 interface, the company is TNW (the Net Works), and I think they also built the Commodore 8010, an acoustic modem for the PET. I have some notes on using the device but have never actually seen one.

Some electronic devices DO have IEEE-488 interfaces built-in to talk to computers, and the communications protocol is the same as on the PETs, you will need to get the data on how to communicate with your device though (like what device number it is, what commands it knows, etc.)

which should be available from the device's manufacturer.IEEE-488 is also used on some Hewlett Packard computers and is referred to as either the HP-GPIB, HPIB or just GPIB (for General Purpose Interface Bus). Even though IEEE-488 is a standard it was not adhered to precisely by Commodore so some 'tweaking' of your programs may be necessary in order to get non-commodore equipment working. (I.E. convert commands to true ASCII)

Like many other microcomputers of the time the PET was not originally designed to produce sound. A few methods of sound generation have been developed but the most popular employs the use of parallel user port pin M which is used to generate a 'square wave' output by setting the 'handshake register' for port B into a free-running mode. Adjustments to the timing of the handshake and the pattern of the 'wave' adjusts its sound and timbre. You can achieve approximately 3 octaves of notes and various noises with this one voice output.

The latest 4000/8000 (large screen PET) motherboards already have a built-in piezo speaker and also have a bell sound accessible with a print: chr$(7)

Sound Interface Diagram (use mono-spaced font to view properly)

 Parallel Port:
                            1  1  1
 1  2  3  4  5  6  7  8  9  0  1  2
 =  =  =  =  =  =  =  =  =  =  =  = 
### ######################### ######
 =  =  =  =  =  =  =  =  =  =  =  =
 A  B  C  D  E  F  H  J  K  L  M  N   Ground  +=====+
                               !  +-----------!AUDIO!
                           CB2 !  50-500K res.! AMP !
                               +-/\/\/\-------+=====+

You can get most of the parts (except the parallel port connector) at Radio Shack, including a low-cost mini amplifier. See below for a source for 12/25 edge board connectors.

The PET was not initially designed for joysticks but a determined user had devised a dual-joystick interface employing the parallel port. This interface allows you to plug in standard Atari/Commodore compatible joysticks….

Interface Diagram  (use mono-spaced font to view properly)

Looking at back of user port         1  1  1
          1  2  3  4  5  6  7  8  9  0  1  2
          =  =  =  =  =  =  =  =  =  =  =  =
         ### ######################### ######
          =  =  =  =  =  =  =  =  =  =  =  =
          A  B  C  D  E  F  H  J  K  L  M  N
          !     !  !  !  !  !  !  !  !     !
          !     !  !  !  !  !  !  !  !     !
port 1->  8     1  2  3  4  !  !  !  !     !
                            !  !  !  !     !
                 port 2->   1  2  3  4     8

Joystick pin diagram =>  5  [4] [3] [2] [1]
looking at back of                    \ /
male connector             9  [8]  7  [6]

The 'fire' button (pin 6) is added by connecting joystick port pins 1 and 2 to pin 6 with diodes, solder each diode from (already wired) pins 1 and 2 to pin 6 (with the banded ends to pin 6).

On the PET the pin arrangement for the IEEE-488 port is:

                            1  1  1
 1  2  3  4  5  6  7  8  9  0  1  2
 =  =  =  =  =  =  =  =  =  =  =  =
###### ################### #########
 =  =  =  =  =  =  =  =  =  =  =  =
 A  B  C  D  E  F  H  J  K  L  M  N

 1 - DIO1       9 - IFC         E - REN
 2 - DIO2      10 - SRQ         F - GND
 3 - DIO3      11 - ATN         H - GND
 4 - DIO4      12 - GND         J - GND
 5 - EOI        A - DIO5        K - GND
 6 - DAV        B - DIO6        L - GND
 7 - NRFD       C - DIO7        M - GND
 8 - NDAC       D - DIO8        N - GND

IEEE-488 Device Connector Pinout:

 +-
 ! ----       (NOTE:  The pin order may look backwards
 !     ---+      but two references list it as such)
 !  1  13 !
 !  2  14 !
 !  3  15 !      1 - DIO1       9 - IFC        17 - REN
 !  4  16 !      2 - DIO2      10 - SRQ        18 - GND
 !  5  17 !      3 - DIO3      11 - ATN        19 - GND
 !  6  18 !      4 - DIO4      12 - GND        20 - GND
 !  7  19 !      5 - EOI       13 - DIO5       21 - GND
 !  8  20 !      6 - DAV       14 - DIO6       22 - GND
 !  9  21 !      7 - NRFD      15 - DIO7       23 - GND
 ! 10  22 !      8 - NDAC      16 - DIO8       24 - GND
 ! 11  23 !
 ! 12  24 !
 !     ---+
 ! ----
 +-

                               1  1  1
    1  2  3  4  5  6  7  8  9  0  1  2
    =  =  =  =  =  =  =  =  =  =  =  =
   ### ######################### ######
    =  =  =  =  =  =  =  =  =  =  =  =
    A  B  C  D  E  F  H  J  K  L  M  N

 1 - System Ground        A - GND
 2 - TV Video             B - CA1
 3 - IEEE-SRQ             C - PB0
 4 - IEEE-EOI             D - PB1
 5 - Diagnostic Sense     E - PB2
 6 - Cass.1 Read          F - PB3
 7 - Cass.2 Read          H - PB4
 8 - Diag Tape Wrt.       J - PB5
 9 - TV Vertical          K - PB6
10 - TV Horizontal        L - PB7
11 - GND                  M - PA2 (CB2)
12 - GND                  N - GND

    1  2  3  4  5  6
    =  =  =  =  =  =
   ###### ###########
    =  =  =  =  =  =
    A  B  C  D  E  F

 A or 1 - GND
 B or 2 - +5v
 C or 3 - Motor (computer controlled +6v for datasette motor)
 D or 4 - Read line from cassette
 E or 5 - Write line cassette
 F or 6 - Cassette Switch Sense (monitors cassette play/ff/rew buttons)

An excellent source for PET compatible edge board connectors as, the 24pin centronics connectors (not to mention just about any other component) is DigiKey Corporation:

DigiKey Corporation 701 Brooks Ave. South Thief River Falls, MN 56701-0677

(800) 344-4539 www: http://www.digikey.com

Call or write and ask for a catalog!

The parallel and IEEE-488 ports both accept 12/24 edge board connectors with 156” contact spacing, the datasette port accept 6/12 connector with .156“ contact spacing.

Side Note: Digikey does not seem to have proper hoods (enclosures) available for the edgeboard connectors, which can make it quite a struggle to remove the buggers once connected. I have found that using 1.25” long by 6/32“ machine screws fit snugly in the side mounting holes, with a matching nut and lock washer it would make a good gripping surface away from the sensitive contacts. These parts can be easily/cheaply found at most hardware stores.

                  +---+ Washer and Nut
  Mounting Hole  !!   !!!--------+ 
                 !!   !!!--------+ Screw
               +--+   !==
Edge Contacts  !      !==  Pins

This is a list of some of the many devices of the PET I am aware of, for many I only know of their existance not how they are installed or used.

• MTU Visible Memory Board - display board that adds a 320×200 hi-resoluion grpahics output to the PET (8000 series is 640×200) - came with a BASIC 'keyboard' graphics package to add drawing commands to your programs.
• Petunia Sound Board - Polyhponic high quality sound - based on HAL Chamberlin's sound projects.
• MTU Sound Board - I believe similar to Petunia
• Composite Video Adapter - Plugs into the parallel port provides composite video output
• CB-2 Sound connectors/amplifiers
• Plotters - i.e. MiPlot, HiPlot?
• Kurta Graphics Tablet - tablet digitizer
• Interpod - IEEE-488 to 64/VIC style serial
• TNW 300 - IEEE-488 to RS-232 adapter
• Votrax Speech Synthesiser - also Commodore branded.
• Programmable Character ROM interface (allows you to program new character sets.
• S-100 Bus Adapter
• 3-G Light Pen - Simple light pen
• CompuThink ExpandaPET or ExpandaMEM - RAM Expansion w/KIM bus for original PET
• RAM-ROM Card - ROM emulator card
• Cluster One / Regent - Networked disk drives.
• Battery Back-Up - For PETs and Dual Disk Drives
• Plexi-Vue - Glare Filter
• Exatron Stringy Floppy - Somewhere between a tape drive and a disk drive…
• A/D Converters and I/O Controllers
• IEEE-488 to Parallel or RS-232 Printer Interfaces
• Full-Sized Keyboard for Original PET