Cirkit serial interface

The Cirkit serial link was used for the Cirkit Prestel link

Reportedly, it did "flourish", but almost nothing else is known.

• Some information fragments are here: Cirkit.

Technical

(information from the documentation with the "Prestel Link" software.)

Prestel link hardware:

• 4Mhz clock from expansion bus is clock for 8251
• Chipset: uses 8251 UART
• I/O ports are:

FADF read/write data
FBDF read status/write control

• Note - Cirkit reportedly also made a "Twin-port" serial interface (which probably used other chipset)

Pictures

• 

  Circuit board, etc.

Manual

Documentation is found on the driver cassette (files HARDWARE.DOC and RSX.DOC, which can be viewed or printed with LIST.BAS). Below are the two DOC files converted to TXT format:

• File:Cirkit prestel link hardware.txt
• File:Cirkit prestel link rsx.txt

Downloads

• Media:Cirkit prestel link tape v1.0a.zip - Drivers & Documentation on cassette

The cassette contains the following files:

• MENU.BAS - Prestel Link, Terminal, Send/Receive File tool
• USER.BIN - RSX Commands 1 (interface)
• PRES.BIN - RSX Commands 2 (prestel)
• LIST.BAS - Tool for viewing/printing the DOC files on Side B
• HARDWARE.DOC - Description of the I/O Ports and cable
• RSX.DOC - Description of the RSX commands (USER.BIN and PRES.BIN)

Specs (from advert)

• Fully compatible with the CPC464, CPC664 and CPC6128.
• Plugs into Disk Drive, through Bus Connector for Disk Drives and other peripherals.
  [Note: On the CPC 464, the "Expansion Port" was called "Floppy Port", this is probably what is meant by "into Disk Drive"]
  [Note: The photo in advert seems to be a fake. It looks like a 2x28 pin expansion for Sinclair Spectrum, re-badged as Amstrad Interface for the advert]
• Can be used to interface to other RS232 devices, such as Modems, Plotters and Printers.
• Baud rates supported 75/1200, 1200/1200 and 300/300
• INPUTS:- Data, one handshake - RS232 compatible
• OUTPUTS:- Data, one handshake - +5 volt positive going Works with all TTL level inputs and most RS232 devices.
• All interface features are software addressable, uses 8251 UART.
• Supplied with full RSX drivers, which may be used in your own programs.
• Not directly compatible with Amstrad CPM.
• Extensive documentation about interface and RSX's supplied on cassette.