SCC card

The preferred way of interfacing the NET software (and other packet radio programs) to the radio is via an SCC card. It is named after the Zilog Z8530 SCC chip that is central in the design. Each SCC chip provides two independent HDLC channels, that can operate fullduplex when an external divider is provided or when the MODEM provides the clocks.

One example of an SCC card is the PA0HZP OptoPcScc card. Its features are:

  • 8-bit ISA PC-card
  • two Z8530 chips providing 4 channels (Z85230 ESCC can be used)
  • clock dividers are provided on all channels (enabling fullduplex use)
  • the interface to the modems is via optocouplers that provide guarding against ground loops in the station and protection against voltage spikes and wiring errors
  • supports vectored interrupt for efficient operation with many channels
  • interrupt selectable from 2-7
  • boards can be daisy-chained to use 1 common interrupt

    • The board is supported in many packet radio programs, including:

  • NET-PE1CHL as described elsewhere on this site
  • the many versions of the NOS program by KA9Q
  • G8BPQ's node software
  • TFPCX (a hostmode TNC emulator) enabling use of SP, GP, F6FBB etc.
  • Linux kernel AX.25

    • Several MODEMs are available with the interface as specified by the OptoPcScc card, including:

  • 1200 baud TCM3105 MODEM by PA0HZP
  • 4800 baud HAPN MODEM by CADAMS and DDS
  • 9600 baud DF9IC MODEM (compatible with G3RUH) by CADAMS
  • 9600 baud G3RUH MODEM by DDS, can be set to other speeds
  • 1200/4800 baud DUOMODEM by PB0AAQ (TCM3105 and HAPN MODEM on a single card)

    • The PA0HZP OptoPcScc cards are used in most nodes in the Dutch packet radio network. Most nodes consist of a 386 PC with 2 or 3 OptoPcScc cards, operating under MSDOS with the NET-PE1CHL software. There are a few Linux-based nodes as well.

    More info about the OptoPcScc, including schematics and board population diagram in EPSON FX-80 printable format, is available from this file: sccprin5.lzh.

    Some info about the 4800 bps HAPN modem technology is available here: 4k8mod10.lzh.

    The schematics and info about the DUOMODEM are in this file: duomod31.lzh.

    To unpack these .lzh files, use lha213.exe or another LHA or LHARC compatible archiver.