PROCESSING THE WORDS

Hilderbay has produced for the Spectrum a printer interface as well as software to run it, including a mini word processor. The black box has 23-way printer plug on the front and a ribbon cable of up to one metre ending in the usual Centronics-style plug. The box has no extender PCB, so any add-ons such as Microdrives must go between that and the printer interface.

The software is a Basic program and a small piece of machine code. The Basic program allows you to set up a series of options which are then incorporated into the machine code.

Tasword can have the printer software inserted so that it uses another printer instead of the ZX printer.

The options on most printers are different but they can offer underline, emboldened or enlarged text using the graphics characters re-programmed to give control characters.

A COPY software routine is also included but not using the COPY command. All other commands are by the use of LLIST or LPRINT. There should be no need to go inside the printer to set up the CR/LF options as they can be set from the software.

It is a very good combination of hardware and software at £45. Hilderbay Ltd, 8-10 Parkway, London NW1 7AA. Tel: 01-485 1059.

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: Housed in the same kind of box as the Morex interface, this vertically mounted unit also suffers from the aesthetic point of view. However, it more than makes up for that by the features it includes. Equipped with two Centronics leads, one short and the other a generous 1.5 metres, it also acts as a printer spooler.

The internal design is messy and the attention to detail during construction looks poor; at least two of the internal straps were in danger of shorting out to IC legs. The chip count is small: an 8255, a 4071 and an unidentified device are all that reside on the PCB. A 3.5mm socket is also provided on the unit; this intercepts the EAR lead to the ZX Spectrum and does away with the hassle of having to remember to unplug it each time you do a SAVE.

Manual: Seven A4 pages cover everything about the interface, including the various graphics dump routines (although quite who would have the patience to wait while a Juki daisywheel printer does a screen dump is beyond me!).

Software: The review sample came with a full driver which resides in normal memory and a smaller mini-driver which lives in the printer buffer. The penalty paid for using the smaller version is that all the control codes are trapped, so specific POKEs must be issued to get the printer to operate in other fonts or modes.

A second tape, together with two sheets of documentation, covered the use of the interface as a spooler. Here the ZX Spectrum is used as a printer buffer for a larger computer. When conventional microcomputers are dumping text files on to a printer, the machine cannot do anything else; in fact, while this review is being printed out by my Apple IIe, there really is time to make a cup of coffee. What's needed is a large memory store into which the entire contents of the text file can be loaded. Control of the computer is then restored to the user while the text is being fed to the printer from this buffer. The ZX Spectrum offers a fairly low cost alternative, by using it in conjunction with the Hilderbay interface.

The printer spooler idea can be taken even further by allowing the ZX Spectrum to perform some post processing on the text that it's storing. One such program is being developed to allow true justification with proportionally spaced text. Developed for Diablo-type daisywheel printers, it unfortunately doesn't allow buffering at the same time... still, you can't have everything.

Price: £99.00 all inclusive.

Summary: For reasons known entirely to itself, the Hilderbay unit declined to operate as a spooler with an Apple DMP, although its performance as a standard interface was flawless. As the great strength of the professional unit is that it can operate as a spooler, this was a little disappointing.

While the interface as it stands is as good as any of the others, it's the possibility of using it as a buffer that makes it stand out from the crowd. If you already own a bigger computer and just use the ZX spectrum for games or for children to learn on, then this interface offers both real printing on the ZX Spectrum and time saving for your bigger machine.

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.