(Simon N Goodwin owns the copyright to this review. Please visit http://simon.mooli.org.uk to find original articles and updates, much new material and his contact details.)

GETTING INTO PRINT

If you've been frustrated by your printed listings, check out this new device from Euroelectronics with Simon Goodwin.

If you've ever spent hours puzzling over a smudged listing from a Sinclair printer then ZX LPRINT could be the device for you.

ZX LPRINT is a small black box, which plugs into the back of your Spectrum where a Sinclair printer would normally go. A socket on the back of the box allows you to plug in a lead linking the Spectrum to a quality dot-matrix or daisy wheel printer.

The unit modifies the workings of the Spectrum ROM so that, while the box is connected, all the text which would normally go to a Sinclair printer goes to the quality printer instead. You can use the standard LUST and LPRINT commands - the box will interpret them without the need to load special 'driver' programs to stop the computer trying to use the Sinclair printer format.

ESSENTIALLY...

ZX LPRINT is made up of two essential sections - a 'parallel port' which allows the Spectrum to communicate with any printer equipped with a standard 'Centronics' interface. Most cheap dot-matrix printers use that interface, and consequently they can be directly connected to ZX LPRINT.

The second ingredient is a 'ghost' ROM memory, similar in principle to that used in the Microdrive interface. When the box is connected, it uses internal electronics to 'replace' part of the Spectrum's 16K ROM. The effect is that the parts of the ROM which used to deal with Sinclair's printer are replaced with machine code to work ZX LPRINT. The computer works just as normal, except LLIST and LPRINT are routed to the quality printer.

There are, however, a couple of potential snags. ZX LPRINT sends two signals to the printer at the end of each line - one to move the print head to the start of the line and the other to wind the paper on. Some printers automatically wind the paper as they move the head back, so that they give double-spaced printout with ZX LPRINT. There is usually a switch inside the printer to stop this happening, but it is a shame that the ZX LPRINT instructions do not mention the possibility. The instructions are actually printed on the back of the interface box, which means that they are rather short although at least you can't lose them!

Another snag is the way that ZX LPRINT treats graphics. All popular printers treat alphanumeric characters the same way, so that it is easy for LLIST and LPRINT to work correctly with letters and symbols. Problems come when you try to send user-defined graphics characters to the printer. You can't send those characters with the LLIST or LPRINT commands, since only a Spectrum printer would recognise them properly.

Almost every printer has a different way of coping with graphics, so that code to handle every variation of user-defined graphics and screen layout can't be built into the box. However, ZX LPRINT can recognise the COPY instruction. The makers supply cassette programs which allow you to COPY to most of the popular makes of printer, by loading appropriate machine-code into the Spectrum's reserved memory. ZX LPRINT will automatically use this code if it is present, allowing you to produce high-resolution dot-matrix screen printouts.

IN THE PICTURE?

ZX LPRINT costs £41.40 including VAT, plus a rather high charge of £12.08 for a ready-made cable. The COPY software is available for most popular printers - each version comes with a demonstration tape which costs £5. The interface is made by Euroelectronics, Montpellier Retreat, Cheltenham, Glos.

At these prices ZX LPRINT is an expensive add-on for a Spectrum, but the price is fair considering the clever design and the cost of a printer to connect to it. If you're sick of 'space-age' Sinclair printouts and you can afford a quality printer, ZX LPRINT is an investment worth considering.

GETTING INTO PRINT

Good as it is for the price, many users are bound to be disappointed with the output from Sinclair Research's own printing device. For those toying with the idea of upgrading their Spectrum system with a professional printer, Henry Budgett takes an in-depth look at the technology involved and the plethora of interface devices now available.

Regardless of what one actually thinks about Sinclair Research's ZX Printer, it's impossible to ignore the fact that it really does work. For the price and performance that it offers there's no equal anywhere. But despite that, there are users who need something a little more professional. Software houses developing programs, small businesses using the ZX Spectrum or just a serious user who demands something better than a sheet of aluminised paper that is, at best, just legible after a few days' handling.

We're fortunate in having a number of commercially available interface units that allow the ZX Spectrum to be connected to the growing range of low-cost printers. In the main, these units convert the signals provided on the expansion connector into those which conform to the industry standard Centronics interface. There are two stages to this conversion: that of altering the electrical characteristics of the output from the ZX Spectrum and that of converting the character codes from Sinclair Research's own internal format to true ASCII.

The alterations to the electrical signals are handled in a variety of ways by the interfaces reviewed here; some use very sophisticated chips to handle the work, others tackle the task by using more of the simple ICs. Only one of the interfaces in this review offered the possibility of connecting to a serial printer but, in theory at least, the problems involved are tackled in much the same way.

All the interfaces were supplied with software drivers of one sort or another (see the individual panels for further details) and in general, these all work by intercepting the ZX Spectrum's printer routine vector. This is the location in memory that stores the address of the routine which controls data being sent to the printer by LLIST and LPRINT. By changing this address to that of the new driver all the data is re-routed through one of the OUT ports to the interface. On their way, each of the characters passes through a 'code converting' routine held somewhere in memory. While the normal alphanumeric codes closely follow the standard ASCII set, all the control codes, predefined graphics and Basic tokens must be intercepted. In the case of the tokens, these are converted back into strings of ASCII letters before being listed. Because many of the currently available printers use sequences of control codes to change character fonts or to select graphics, provision must also be made to allow these codes to be sent without being trapped.

The test equipment to which the various interfaces were connected comprised a Tandy CGP-115 four-pen plotter printer and an Epson FX-80 dot matrix printer. Unfortunately, the Epson turned out to be 'Dead on Arrival' and the author's Apple Dot Matrix Printer was substituted. As this printer is based on a TEC chassis, it proved impossible to check the graphics dump facilities on all but one of the interfaces. However, there is no evidence to suggest that the software provided wouldn't operate correctly with the appropriate hardware and indeed, the Kempston interface unit has been seen elsewhere to function perfectly with both the RX-80 and FX-80 printers.

Hardware: This unit was the only horizontally fitted interface of the range under review. A single PCB is sandwiched inside a small, standard 'plotting' box; the result is not particularly attractive. A detachable ribbon cable just over one metre in length, plugs on to the rear of the unit and although no key is provided at the unit end, it would be difficult to plug it in the wrong way around. On the review sample, the plastic frame of the PCB- mounted header had been cracked but no problems resulted.

Interestingly, this interface does the COPY processing internally - a ROM contains suitable software for the printer chosen. Of the six remaining ICs, two had had their idents removed and as they all appear to be common devices, the reason may be that they are rejects - which could bode ill for long-term reliability.

Manual: it seems almost churlish to call a single side of A5 paper a manual! However, further information is provided 'on-screen' once the software is loaded. Interestingly, there is no mention of LLIST anywhere, yet it works!

Software: The driver consists of a short (109 byte) routine that forces itself to the top of memory and then resets RAMTOP. All the rest of the processing is carried out by the ROM in the interface. To prove that it really works, the tape includes a demo picture to dump - one of those highly magnified views of a pimple! The COPY program supplied with the review sample was suitable for driving the Epson range as well as the Star DP510 and 515 printers and the Shinwa CP80.

Alternative software is available for the Seikosha GP100 and GP250X printers, the Microline series and the latest offering is for the Tandy CGP- 115 and MCP40 printer plotters which can provide (very slowly) copies in four colours. A new version of the interface is due out shortly with a range of software built in as standard.

Price: £34.50 plus £10.45 for the cable.

Summary: Despite its rather shabby looks, the LPRINT worked well and the provision of software in ROM makes for faster operation. When your author passed comment on its appearance to a friend he replied that he expected interfaces to look like that! The price of the cable is very high and it might be worth making your own. But apart from that it offers good value for money.

OVERALL SUMMARY

Of the three standard units - Kempston, ADS and LPRINT Mk II - the latter inherently has the advantage of on-board software, giving it greater speed and more flexibility. Between the other two the ADS is slightly the neater but the Kempston is supplied with a better range of driver software and virtually every- thing works with it directly.

The two 'up-market' units both have advantages in their own ways. For serial printers there is no option but to choose the Morex unit. It offers parallel as well and comes complete with an excellent manual; if pushed, it probably represents the 'Best Buy'. It's a shame about the packaging - fit a nice box around it and you'd have a real winner.

The Hilderbay unit stands or falls on its usage. If there is a need in your life for a printer buffer - and you already have a ZX Spectrum - then this interface will satisfy both requirements. It's also rather cheaper than having to fork out £230 for a 64K printer buffer! As a standard interface it offers nothing special, apart from direct compatibility with all of Hilderbay's software.

There are other printer interfaces around - for instance, Softest offer one especially for the Tandy CGP-115. However, as it's a serial-only interface and all the others seem to drive the device quite well, I'm not sure about its value. Unfortunately, the promised review unit failed to appear by the deadline for this survey so no further comment is possible.

The interface you choose should really reflect the uses to which it is going to be put. If all you want is a simple-to-use means of getting a proper printout then the ADS, LPRINT Mk II and Kempston units offer just what you are looking for, provided that the driving software is available. More sophisticated users will find the Morex unit well worth a look and those with other computers to support will find the Hilderbay device attractive from the printer spooler viewpoint.