RS423 Interface (Pace) Review | A&B Computing - Everygamegoing

A&B Computing

RS423 Interface
By Pace Ltd
Acorn Electron

Published in A&B Computing 3.04

The long-awaited and much heralded RS423 interface for the Electron goes on-line

RS423 Interface

Acorn always intended the Electron to have an RS423 interface. The operating system (FX) calls were 'reserved for further expansion'. It's just taken over two years to make it happen. PACE are the heroes of the hour. They have taken the Acorn-designed hardware and made it a viable and practical product for Electron owners.

Acorn are to be applauded for swallowing their pride and cooperating with established BBC communications experts from Bradford. PACE's contribution is the Commstar software, an Electron version of an established piece of BBC firmware and the marketing of a complete communications package, interface, software, cables and Nightingale modem, for £149.00.

Plug In And Go

The hardware consists of a printed circuitboard containing just seven chips, including the socketed 16K Commstar EPROM. The main interface chip is the SCN2682 DUART. The neat plastic housing is a very tight fit indeed in a Plus One cartridge socket. Once slotted in, this is of course an advantage. The RS423 cable is soldered to the PCB at one end and plugs via a DIN into the modem.

Nightingale supports 1200/75, 75/1200 and 300 baud transfer rates. These are selected from the front panel. These are the standards needed to operate with Prestel (Micronet 800), all the major bulletin boards, British Telecom Gold (Microlink) and business services such as One to One.

Two LEDs display power/data and carrier detect/line hold. In its present form the package does not support autodialling, although an add-on board is a future possibility. Therefore there is also a modem connect button on the panel. This is pressed after dialling a remote computer manually and listening for the carrier.

In the communications package we have a 'plug in and go' situation. Just dial a number! The serial port opens up so many different services and Commstar can deal with most. The viewdata terminal deals with Prestel and 1200/75 bulletin boards. Commstar deals with sending and receiving Prestel frames and downloading telesoftware. The ASCII terminal deals with 300 baud bulletin boards, with British Telecom Gold and other remote computers, including other micros. Chat mode even allows user to user conversation. Finally, you can use Commstar facilities to send files of ASCII data to another computer with error checking built in.

Nor is the RS423 interface just a means of using a modem. The serial interface can be used with comms software to connect directly to another micro. There are even networks based upon the serial standard. Serial printers can now be used in association with the Electron. Many daisywheel printers have serial interfaces only. The RS423 also opens up control applciations with the very popular Penman plotter/digitiser/mouse combination firmly in mind. The Commstar software itself can be removed and other application software inserted (EPROM types 274, 27128 or 27256 can be used) into the single socket on the interface board.

Are They Ready For The Electron?

Beyond the telephone plug on the wall behind the computer desk lies an ever-expanding range of communications services. Are they ready for the Electron? What's available? Are we welcome? Certainly the latter. The bulletin boards are notoriously friendly and encourage people to get involved.

What about Prestel? All the information services are obviously available. Micronet 800 has already started an Electron section. As this piece went to press, it had one letter and a notice stating that the service had been withdrawn. They needed an Information Provider. It's early days yet and information providers galore will no doubt surface.

We tried some BBC telesoftware. Wilf and Formula One were slow, viscous even! Antares like treacle. Firebird's Harvey Headbanger provided a nice screen of cocktails but nothing else. Bruce Everiss' Wet Zone worked, but lost its edge. But a ray of hope: Diamond, a bit like Repton shoving rocks around, lots of screens, a difficult and challenging game. So it can be done. Free telesoftware is a big pull so here's hoping Micronet lend support. Perhaps to begin with, some indication of BBC software which is suitable for the Electron would do.

We had no trouble with bulletin boards at all, and even downloaded a complete satellite weather picture off Swafax. British Telecom Gold and One-to-One responded as per usual so the business user can contemplate an Electron communiations workstation at well under £400.


PACE's Andy Hood has done a wonderful job with Electron Commstar. It's easy to use through full screen menus on which you highlight options and through facilities accessed via function keys within the terminals. Commstar deals fairly well with the Plus 3 and ADFS and the Prestel emulation is outstanding.

The PACE documentation for both Nightingale and Commstar is of the highest standard, packed with information on how to use the software and with technical asides and appendices for those who want to do their own programming and need to know the 'how' behind the friendly front end of Commstar. All the relevant FX commands are fully documented for DIY communications programmers. There's a full glossary and 'getting started quickly' sections for beginners.

Buffer Control

Commstar provides comprehensive control over the input and output buffers through which data passes, on its way to the modem or from the interface to the filing system. A disc buffer is especially necessary with Plus 3 disc operration because ordinary spooling can result in lost data. The extended buffer remains restricted to 17K but at times when large amounts of data need to be transferred, it is possible to save the buffer, reset it and start again without corrupting incoming data. The buffer can be loaded for transmission or saved after collecting data from the RS423. You can also view the buffer (with hardcopy if required), reset it and wipe it.

The ASCII terminal can be configured for different data formats for both send and receive. Echo, line feed, XON/XOFF and filter can be switched on and off as required. Any screen Mode can be used by the terminal and the printer can be toggled on and off. Function keys remain programmable and *EXEC files can be used to initialise Commstar.

Prestel Emulation

Commstar's Prestel emulation is absolutely excellent. We were ready to be disappointed but the Mode 4 screens make good use of double height characters, reversing out (black on white blocks of background) and is generally good to look at. The screen display cracked up a couple of times but this was probably due to data corruption on the telephone line. The screens are sharp and attractive in their own right. It's almost preferable as an information display to the sometimes weak teletext colours of a BBC display.

All the usual Commstar Prestel facilities are available, tagging of frames for later recall, retrieving tagged pages, clearing tags, return to previous page, copying a screen image to disc, revealing hidden text, loading frames from disc, downloading frames from Prestel (including telesoftware), printing a frame. The print option includes full graphics on an Epson compatible printer.


The Electron Communications Package is what it says, a serial communications bus which opens up vast new areas of interfacing with peripherals, other micros and, of course, a vast array of services provided on the public telephone network.

PACE have given meaning to the interface with an Electron version of Commstar with which any user can be well pleased. The Nightingale doesn't have all the features of the latest modems but remains a staunch performer in association with Commstar.

Access to the service and software on Prestel and on bulletin boards boosts the Electron's scope for providing both entertainment and business facilities such as electronic mail. The RS423 interface brings the Electron up to date and ready for the future.