SOFTROM CORRECTIONSConcerning your article on the SoftROM by Mike Lord. Having built the project, I discovered that 64 x 1 (4164) DRAMS would not work in the circuit as given. The problem arises from the Z80 refresh system which only puts out a 7-bit refresh address (A0 to A6); 4164s require an 8-bit refresh (that is, a 256 refresh cycle).
My solution was to ensure that address lines A0 to A6 are strobed by RAS and A7 to A13 by CAS. A14 and A15 are 'don't care'.
Unfortunately, anyone wishing to use this project to upgrade to 48K will not be able to do so without changing the refresh system.
Also, when using the SoftROM with a 48K Spectrum, I would recommend an external 5v supply using the 9v line from the edge connector to drive it.
I've designed a double- sided PCB for this project; any readers interested should write to the address below.
P Giblin, nn xxxxxx xxxx xxxx, xxxxxxxxxxx, xxxxxxxx xxnn nxx
INCOMPATIBLE LPRINTAlthough I find your magazine generally very good, one of your articles contains an inaccuracy which has caused me a lot of problems.
In the article 'Getting into Print' you state that the ZX LPRINT works with the ZX Microdrive, which is not true at all. I have both these items and they will not work together, or rather the ZX LPRINT works, but the Microdrive won't while the ZX LPRINT is connected.
I contacted Euroelectronics (makers of the ZX LPRINT) and after much evasive talk the company finally conceded that the product is incompatible with the Interface 1 unit. They do offer an adaptor at £4.50 which allows the ZX LPRINT to be switched out when the Microdrive is in operation; but will this allow such things as CAT#3;1 - I doubt it!
David Leckie, Fort William
ANT ATTACKSI'm writing to you about this fantastic competition which you held, together with Prism. When I read the rules I hastily got out my copy of (original) Ant Attack and proceeded to battle my way through the different levels, finally reaching the magic tenth level. Great, I thought, only another three times and I've cracked it. But wait what's this, on the second time she was in the same place. So off we went again, the intrepid rescuer in search of his damsel, and eventually after about twenty attempts I finally found all four places (The Forum, The Oxymine, Artant's Villa and Droxtrap, by the way). Now all I had to
Finally 30th March arrived and I quickly grabbed The Daily Telegraph off the doormat and hastily scanned the classified ads. Alas I couldn't find it, so I browsed through all the pages as the time slowly ticked away. But still I couldn't find it so I rushed out and bought a copy of The Guardian and there on page 25 sat the ad. I quickly read it and loaded up my copy of (original) Ant Attack yet again, and searched high and low for the mysterious object, after about two hours I found the box marked 'AMMO'.
Now, I thought, I just have to wait until noon to ring through my answers. But oh no!! - Telecom had different ideas. Every time I rang the number given I got the engaged tone. After 12:45 I rang the operator: "all lines to London are engaged please try later" was the reply - I could have screamed. All my hard work to waste and still at 13:45 the line was engaged. Time to give up, I thought.
So that was when I decided to write this letter. Don't you think it's a bit unfair for the people who live outside London, giving us no chance of getting through. Maybe a later time would have been a little better, you know! Maybe when no one is at work and all the lines are not busy. Somebody from the South probably won the competition as us poor Northeners could not get a reply.
Next time, if there is one, give everyone a fighting chance.
I now go to ceremoniously burn my copy of Ant Attack kindling it with the second copy of YS (I have to take it out on something and it was, after all, the root of all my frustration).
Andrew Hatton, Macclesfield
First, our thanks to The Daily Telegraph for not publishing the ad in the Northern Editions of the paper - nice one chaps! Actually the first call to come in wasn't from London. However, a wrong answer did give it to the second caller - from London. Apologies to all those who felt aggrieved at hearing only the engaged tone. With (according to BT) something like 10,000 callers trying to get through, it was inevitable that 9,999 wouldn't be able to make it at any one time. The odds for winning with this kind of telephone tombola must, of course, be the same as postcards out of a hat and we hope the approach gave the competition a refreshing twist. Ed.
PARDON THE PLUGAs the author of the first
book about the QL, The Sinclair QL Companion, I
must point out that Andrew
Pennell is wrong to compare
SuperBasic with Pascal.
SuperBasic has little in
common with Pascal, but
shares a great deal with Algol
68. All this is explained in
more detail in the QL Companion. |
In the QL Companion I refer to Seymour Papert (author of Logo) because his ideas on programming and computers are relevant to any discussion of structured programming. I have always felt that computers andprograms should be kept away from computer studies departments, and Sandy Dewhurst's philistine review of computer education texts reinforces that view. When one reads on the one hand he cannot cope with Papert, and then finds that "The Spectrum is quite a unique machine...", all is explained.
Boris Allen, Bramhall
BETTER SOUND & VISIONI've discovered a simple way of modifying the Spectrum to output a signal suitable for the Video In socket of a VCR or TV. The effect on picture quality is startling and it also enables you to run Spectrum sound through to your TV.
1. Remove the five screws from the base of the Spectrum.
2. Carefully lift off the keyboard and leave it resting on the front half of the PCB. You must be gentle to avoid damage to the ribbon connectors.
3. You'll see a silver box on the top left-hand comer of the circuit board. This is the modulator (it has the word 'Aztec' written on it). Two wires go into the left side of the modulator. You'll be soldering the inner core of a length of coaxial cable to the one nearest the rear of the computer (the one which disappears into a polythene insulator).
4. Strip 1½ inches of the outer insulation from the coaxial cable and twist back the surrounding wire. Cut the twisted wire into a ½-inch length, dip it in flux and tin with solder. Strip back just under ¼-inch of the insulation from the inner core, dip it in flux and tin it.
5. Solder the inner core of the cable to the wire which enters the modulator nearest to the rear of the computer.
6. Solder the outer sheath to the outside of the aerial socket.
7. Lead the cable out of the hole provided for the TV socket and carefully replace the screws.
8. Put a BNC plug on the other end of the cable and, hey presto, you now have a composite video output on your Speccy.
1. Remove the jack plug in the computer MIC socket. You'll have to cut it off because it's a sealed unit.
2. Solder the original wire and another wire to a 3.5mm jack plug. This will leave you
with two wires coming out of
the plug. |
3. Attach a suitable plug to the loose wire. Its type will depend on the sort of sound input socket on your VCR/TV.
4. Push the new plug into the Sound In socket on your equipment. When you select Video the sound should come through the Tv/monitor speaker.
I hope your readers will find this interesting. All the best.
NE Salt, Crayford
A PEEK BEHINDHaving just read the third issue of Your Spectrum, I felt compelled to write regarding the masterpiece of journalistic misprint on page 29, entitled 'A PEEK in Time ...'.
First of all, the traditional method of PEEKing 2-byte system variables appears to have been extended in your opening paragraph:
One multiplied by 256, anyone? A minor point perhaps, but since the whole point of the exercise is to save time and use, 'two less bytes of precious memory' (not a major consideration, I'd have thought, even on a 16K Spectrum) but perhaps one still worth mentioning.
This little gem is immediately followed up by the real killer:
PEEK n+1*256+PEEK n
Let me see now ... by my reckoning, that reduces to:
2*PEEK n + 256
which is not the same thing at all!
Turning now to that listing with the wonderfully spaced line numbers, the first routine translates to the general form:
PEEK (n+1)*256 + PEEK n
... and the second to:
PEEK n+256 * PEEK (n+1)
Oh look Daddy! The clever man has written the line backwards. That's bound to make it faster, isn't it?
Captain Critical, Dartford
OK, humble pie all round (again). Mr Mada's theories are obviously slightly off- track. But, as Ian points out at the end of that piece, the only reason the routine is slightly faster is because the brackets have been removed, not because it was written backwards. Anyway, consider yourself given a Silver Train-Spotter award.
STANDARD CONFUSIONThere seems to be some confusion in your article on the Spectrum RS232 Interface (Page 29, YS issue three). The problem must have occurred because of the non-standard labels that Sinclair Research has used. Your reviewer claims that the interface is non-standard, but this is not the case - he's just wired the RS232 back to front (I made the same mistake myself). The Interface 1 manual states the
following connections for the
As you can see from the table Sinclair Research has named its connections according to the place they go, not what they are. These unusual names have confused everyone I've met who has tried to use the RS232.
I've had a Speccy talking to a CP/M type computer for a couple of months now and communication is bi-directional at 9600 baud. The only problem is that the expensive machine has a non-standard handshaking arrangement, which forced me to make up my own lead rather than be able to use Sinclair Research's.
Jon Ritman, London N13
Hmm, the Bear Bovver person, if I'm not very much mistaken. Thanks a lot, Jon, for pointing out the error of our ways. Ed.
NURD OF THE MONTHPlease, I am interested in your magazine Your Spectrum.
Please forward the magazine Your Spectrum for 1983 numbers 2, 3, 5, 6, 8, 10,11 and 12.
L Vilfan, Bled, Yugoslavia
We'd love to send you the missing copies from 1983 - trouble is, we weren't around then. By the way, what's wrong with issues 1, 4, 7 and 9? Ed.
PRINTING PROBLEMSI must first congratulate you on the production of an excellent magazine devoted entirely to the Spectrum. I welcome such a magazine as other Sinclair mags tend to be aimed at a slightly younger readership who wish to spend time keying in programs and nothing else. However, I digress.
My main reason for writing this letter to you was to highlight a point arising from reading your excellent Issue 3.
There was an article on page 9 about the new Kempston printer interface in which Peter Shaw said that apart from the Fuller Printerface, the Kempston
was the only one with
software built-in. Not so!!!
Euroelectronics produce an
interface LPrint III which not
only has all its operating
software built-in but includes
an RS232 as well as a
Centronics interface as part
of the package. Even better
for those of us who, after
buying a dot matrix printer
are a little short of those
green things, is the fact that it
costs only £36.00.
Admittedly that does not
include a cable but for those
who are not able to make one
up they will provide one for a
charge which still does not
bring it up to the cost of the
Steve Brokenshire, Bridgend
Sorry Steve, when writing that piece on the Kemmy interface, the LPrint III had not been brought to my attention. Point taken. You know, I'm rapidly going off this humble pie.
GILDING THE LILYI would be grateful if you could supply me with the following information. Are there any software packages for the ZX Spectrum which enable the user to produce screen displays of 42, 46 or 51 characters in each row and, if so, where would it be possible to purchase such apackage? I really enjoy your magazine and I am glad to hear that you have gone monthly.
Dermot Connelly, Co. Londonderry
Timedata have recently released a utility called HI-T which gives various screen formats for the Speccy. See Frontlines for more details.
IMPORTANT INPUT PORTSI have recently seen a number of comments in the Spectrum orientated press about the values returned from the keyboard input ports. That the 'unpressed' value in some machines is 255 and in others is 191. I decided to investigate my own machine which is a Series 3 model, so my findings may not apply to other Spectrums.
Rather than just use PRINT IN 32766 (or whatever) I wrote a little program which initialised the screen and then, from within as fast a loop as I could devise, continually updated the value read from all eight keyboard ports as well as the current PEEK 23560 value and INKEY$.
The results were not what I expected. Sometimes the 'unpressed' value from all ports was 255, sometimes 191; and sometimes the values flickered between 255 and 191. The variation (of 64) has to be due to Bit 6, which (if I read my Spectrum book correctly) represents the EAR socket. Is the CPU continually testing it? The flicker seems to be the same as the red/cyan border change that you see when about to LOAD and the tape has not been started.
Mike Minchin, London W11
This is a problem which a lot of software houses kicked up a fuss about when Sinclair released the issue 3 machines last year. The problem cannot be cured however, unless anybody out there has some suggestions?