During the course of 1983 we will increasingly be seeing software available in EPROMs and ROMs, as the basic production costs fall and the general awareness increases. An EPROM programmer is an essential device for anyone wishing to put their own software into EPROM, so we have taken a look at the current state of the market. Two companies have kindly supplied machines for review. No background information on EPROMs or ROMs is given, though you may like to refer to page 16 of the March 1983 Hobby Electronics magazine which explains the technology quite clearly.

The market for EPROM programmers can be identified mainly as: small businesses, education, an increasing number of hobbyists, and software pirates! The ease with which EPROMs can be copied illegally is rather disconcerting, since it will potentially lead to less professional software being produced.

Vacant sockets inside the machine, situated adjacent to the Operating System, are generally referred to as the paged ROM (or sideways ROM) sockets. However it is possible to put a variety of things into EPROMs in these sockets. Basic programs, data files etc. can all be stored, then used by typing *ROM. After an *ROM command subsequent 'read' operations such as LOAD"" will read from the Language ROM sockets, instead of the cassette or discs. (The *ROM command is only available on the series 1 OS).

Supplied By: ATPL, Station Road, Clowne, Chesterfield. S43 4AB.
Price: £120 +VAT, inc. P&P
Includes: Software cassette, all connectors, manual.
EPROM Sizes Usable: 4,8,16k bytes (note: kbytes, not kbits)

The ATPL unit is very well presented indeed. With a well written, well printed A5 manual (27 pages); a cassette wallet containing one cassette with all required software; and the device itself ready to plug in. It connects to both the 1MHz Bus via a 34-way ipeedbLock connector on ribbon cable, and to the power output socket on the Beeb (make sure yours has one fitted).

The software used to control the programmer is on the cassette and must first be loaded and executed. The programming related functions are: Blow, Read, Verify, Clear. 'Blow' programs an EPROM from RAM contents; Read reads an EPROM's contents into RAM; Verify checks that the EPROM has programmed correctly; Clear checks that the EPROM is blank. The Blow command automatically carries out a 'clear' check before programming, just in case you've accidentally inserted an EPROM which is already programmed. I would have overwritten several EPROMs were it not for this safety check.

I was very impressed with the software when I first received it, and remain impressed after using it a great deal. The software is written entirely in machine code and a full assembly Listing (the source code) is provided both as a 5 page listing in the manual, and also on cassette. The fact that it is on cassette means that it can be loaded and re-assembled at a new location. I had to re-assemble it at 81900 in order to use it from discs, for which the instructions are given in the manual. It could of course be located at the top end of memory. The software rates highly on ease of use, with commands to do just what you need. In addition to the four main commands, operating system commands starting with an asterisk are recognised and carried out. Thus, data to be programmed into the EPROM can be loaded from disc or cassette with *LOAD giving the RAM location at which it is to be loaded.

ALl that has been mentioned so far is the programming capability, but the ATPL device has another side to it as well. Any Basic or machine code program may be programmed into one or two EPROMs (a maximum length between 4-32k long) and then placed into either or both of the two special sockets underneath the unit. This program may then be loaded and automatically executed merely by pressing BREAK. It only takes a second or two for the program to load and execute, so speed is comparable to discs. Four switches are provided on the top of the enamelled metal case which are set accordingly for 0S 0.1 or series 1, Basic program, machine code program, or no program at all. Nothing else needs be done. With the switches set and the device plugged in, switching on the power to the BBC micro will result in the program being loaded and executed in an instant. In order to achieve this 'auto run' facility, it is necessary to take a machine code routine supplied on the cassette and program it into an EPROM.

This caused me some initial delay because I didn't know I needed the blank EPROM. However, ATPL do state this on their order form and in their data sheets and can supply a suitable device. It is worth noting this, though if you order straight from a magazine and without seeing an order form, remember that you need a 2732 EPROM.

Only one program may be in the device for auto-run at any one time. The use of the power supply socket, used by many types of disc drive, cannot be used for both programmer and discs at the same time. ATPL rightly point out that not many people will want to use both. The connecting cables on the unit are very short and make it difficult to position conveniently for use. It can only sit very close in front or to the right of the machine. The most obvious disadvantage is the cost, at about £138 inclusive, it is beyond the reach of most 'hobbyists' who are merely interested.

Supplied By: MED, 640 Melton Rd., Thurmaston, Leicester LE4 8BB
Price: £79.90 fully inclusive.
Includes: Software cassette, all connectors except mains plug, instructions.
EPROM Sizes Usable: 2,4k bytes only.

The MED unit itself is well made, but falls short of the ATPL unit in many ways, though it must be pointed out right at the start that it is much cheaper too. The documentation is poorly presented as A4 copies of dot-matrix printer output. However, the content is good enough to help an experienced user to cope with the software.

The programming software is not at all as easy to use, requiring a Lot more thought and understanding. However, its relative complexity includes the possibility of reading or writing any specified part of the EPROM, whereas the ATPL unit deals only in terms of the entire EPROM at once.

Because there is only a capability to program 2k and &k EPROMs, its use for programming EPROMs for the BBC micro is somewhat limited, though for other micro-electronics applications such as in older computers like UK101, PET, etc. it is perfectly adequate. The future of programming EPROMs for the BBC micro is likely to be with 8k and even 16k devices. However, MED have informed me that they are going to produce an add-on to cope with 8k EPROMs and possibly 16k eproms. Since there is no auto-run facility at all on this unit, it is not possible to immediately use an EPROM which you have programmed for the BBC micro. Although MED have successfully placed a &4k EPROM in one of the internal ROM sockets, it was necessary to use an extra machine code routine in order to transfer the EPROM's contents into RAM. All in all, a rather untidy and experimental method at present.

The two machines are not really aimed at quite the same people as far as I can tell. The ATPL unit is useful to those wanting to program EPROMs quickly and easily, and/or to use them for the BBC micro. The MED unit seems more of an investigatory and development device, but for producing EPROMs for use with other machines... for which it is very good.

Finally, the difference in size of EPROM which can be programmed is a major difference between the two, but bear in mind the following: although costs are falling rapidly, a 16k eprom still retails at about still retails at 4 to 5 times the price of an 8k EPROM.