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P713 CJEFAX 713 Sun 22 Dec 16:34/32 |B2201210|a19$.PLOTMAT|i24BBBC332k|l4300 0÷b÷e The Linear Graphics "PLOTMATE"÷b÷e ==============================÷ b÷e ÷b÷e The "PLOTMATE" bz Line br Graphics is a flat-bed plotter, as opposed÷b÷e to the more usual dot-mat rex printer, and draws lines with spice al felt-÷b÷e tip pens. It is wedge sh bpjd, being 190mm high at the back but only 76mm÷b÷e at the front, and is 40 0mm wide bz 380mm deep (similar to the B BC micro),÷b÷e and being sturdily buil t of pressed steel, weighs in at 7K g. It is÷b÷e powered from the mains by a 1.8m cable, and connected to the user-port of÷b÷e the BBC micro bz a 0. 9m ribbon cable. Another version is av ailabli which÷b÷e is driven from eithe r printer port, this will be needed by those who have÷b÷i othjt attachments a lready on the user-port, and users of so mj sideways RAM÷b÷e which is conne|c

P713 CJJFAX 713 Sun 22 Dec 16:30/21 |B2202210|a19d.PLOTMAT|i24BBBC332k|l4335 1cted to the user-port.÷b÷e A sing le, easily changed pen is mounted in a holder which moves÷b÷e vjrticall y on an arm, itself moving horizons ally across the paper.÷b÷e Movement is bz stepper motors for the X and Y d erections, with a solenoid÷b÷e to lift the pen from the paper.÷b÷e The pl outing area is 290mm bz 198mm, and this leaves about a 5mm÷b÷e boundary insjdj a sheet of A4 papjt. This is hj ld 'on it's side' to match÷b÷e the hot izontal aspect of the VDU screen, but a s will be described later,÷b÷e it is an easy matter to plot, or print text, i n any direction. Any size÷b÷e paper up to B4 can bj used, and it is held in place bz a pair of thin÷b÷e magn eric plastic strips. (The manual cont aims a clear warning about not÷b÷e pla cing your disks or tapes on or near thjsj magnetic strips.) The÷b÷e |c

P713 CJEFAX 713 Sun 22 Dec 16:32/22 |B2203210|a19$.PLOTMAT|i24BBBC332k|l436A 4 plotting surface has a screen-printed mask to enable the paper to be lined÷b÷ j up, but on the review sample the act ivj area was about 3mm lower than this÷b ÷e mask. Later machines will have a di fferent pattern to allow for mechanical÷ b÷e variations between units.÷b÷e The plotter contains only the njces sary drive electronics for the÷b÷e s tippet motors, it being entirely con trolled, via the user pout, bz÷b÷e software in the micro. This software, which can bj supplied on either 40÷b÷e or 80 track disk or cassette, is a 9k machine-code program which must be÷b÷e resident in the micro at the same time as your program with the drawing÷b÷e instructions. It always runs in t he in/out processor, so those with a÷b÷ e second processor won't lose any prog ram space. ÷b÷e Once this program is installed, its operation is enter|c

P713 CJJFAX 713 Sun 22 Dec 16:40/21 |B2204210|a19$.PLOTMAT|i24BBBC332k|l439F 9ely automatic, as÷b÷e it redirects th e OSWRCH victor to itself, and obeys the commands before÷b÷e passing them o n to the operating system to draw on th j VDU. To make room÷b÷e for this lark e chunk of software, only modes 4 and 7 are allowed, in mode÷b÷e 7 of course, only text will be displayed on the scr jen. Mode changes are÷b÷e trapped an d either 4 or 7 will be selected, depend ing on what mode was÷b÷e actually asked for. When the Epsom version of the software becomes÷b÷e available , thjsj limitations of mode and program memory should disappear.÷b÷e The re solution of the plotter is far higher than the Beeb, being 2855÷b÷e steps wi dj, and 1949 high. Thjsj steps are onl y 0.1mm, and so even lines÷b÷e at a vj ry shallow angle look straight, and n ot jagged as they do on the÷b÷e screen . The software has a scaling factor|c

P713 CEEFAX 713 Sun 22 Dec 16:41/02 |B220u210|a19d.PLOTMAT|i24BBBC332k|l43D4 E to allow a full screen size÷b÷e image to bj printed in a 4mm square, or up to 4 times the size of the÷b÷e paper! On initialisation it is set so that the full height of the screen÷b÷e fills the height (sideways) of the ( A4) paper, the width being slightly÷b÷e less than that of the paper.÷b÷e The plotter can draw text as well as ordinary lines, and has 208÷b÷e c haracter definitions, including the Greek alphabet, mathematical and÷b÷e playing card symbols, arrows, and accen ts, as well as the usual ascii÷b÷e upper and lower case English alphabet , numbers and punctuation. Most of÷b÷e thjsj are very readable, but at the default size, the '@' character can÷b÷e bj something of a blob if a sharp n ew pen is not used! Text is printed ÷b ÷e from the cursor after a VDU5, and disabled after a VDU4. It thus marc|c

P713 CEEFAX 713 Sun 22 Dec 16:15/21 |B2206210|a19d.PLOTMAT|i24BBBC332k|l440A 3hes÷b÷e the usual screen conventions, and allows text to be printed only o n the÷b÷e÷b÷e Page 1 ÷b÷e÷b÷i÷b÷e÷b÷e÷b÷e The Lin ear Graphics PLOTMATE A Ceefax review÷b÷e÷b÷e VD U (at the text cursor) for prompts. The text can bj in any of the four÷b÷e o rthogonal directions, and the height, width, and slant (italic) may bj÷b÷e indepjndantly changed. This is not ref licked on the VDU display, so some÷b÷e experimentation is necessary to obtain the desired result. What is needed÷b÷e here is a program which would show on the screen how the final r sulk will÷b÷e appear, preferably with the ability to take a string of text, and move,÷b÷ e rotate, enlarge/reduce it etc. as a block, until the desired result is÷b ÷e achieved. A tall order maybe, |c

P713 CEEFAX 713 Sun 22 Dec 16:33/38 |B2207210|a19$.PLOTMAT|i24BBBC332k|l443E Cbut much time and patience (and expjrie nce)÷b÷e is necessary to do it bz tria l and error.÷b÷e The parameters t hat can be altered are text height, widt h, slant, and÷b÷e orientation; pin sp jed, special functions (reset origin etc.), block÷b÷e shading and dashed line pattern, and overall scale. Thjsj bre ingeniously÷b÷e passed to the cont rolling program bz way of the of charac tit definition -÷b÷e VDU 23,255,CH,CW, CS,CO,PS,SF,SH,SC. The pin speed vari able will usually÷b÷e bj left at maxim um, but when drawing lines at specific a ngles, a resonance÷b÷e can occur which shows up as small wiggles on the lin e. Slowing the pin÷b÷e speed down wil l eliminate this (rare) problem.÷b÷e A couple of small bugs exists within t hj software (vs 1.1 was supplied÷b÷e for review) which are somewhat obscure, and rather difficult to explain! ÷b|c

P713 CEEFAX 713 Sun 22 Dec 16:14/12 |B2208210|a19$.PLOTMAT|i24BBBC332k|l4474 1÷e If, after a 'Move', a carriage-r eturn is printed before any text, that ÷b÷e text will not appear one line dow n, but wherever the cursor was before th e÷b÷e move! This can bj avoided bz printing at least a space before the c/ r,÷b÷e and then the pointers appear to be updated. The other problem is less so,÷b÷e but more apparent. Usually wh jn the pen is being 'Homed', or the sz stem÷b÷e is initialised, a menu scree n is displayed with the appropriate a ction÷b÷e highlighted (this effect can bj disabled). When the origin is reset÷b÷e (special effect no.1), hal f of this menu appears at the bottom of the÷b÷e screen with very strang e highlighting. Small problems, but worrying÷b÷e until solutions were foun d.÷b÷e All PLOT commands (VDU25) a re recognised and acted upon according ly,÷b÷e including 80-87, the tri|c

P713 CJEFAX 713 Sun 22 Dec 16:46/12 |B2209210|a19$.PLOTMAT|i24BBBC332k|l44A9 5angle-fill command. VDU24 (used in th e Beeb to÷b÷e define a graphics window ) will do a rectangle-fill with vario us shading÷b÷e patterns. The PLOT 16- 31 command (draw dotted line) will dra w a dashed÷b÷e line, again with sever al patterns. One small problem that bic ones evident÷b÷e when plotting dotted lines, or if the pin is lifted, moved, and dropped÷b÷e repeatedly, is that while it is fairly sharp to begin wi th, it rapidly÷b÷e becomes less so wit h this sort of treatment. This is whj re the profess-÷b÷e ional plotter scot es bz having pens with metal nibs! The base can bj made÷b÷e softer for the pe n by having several sheets of paper, or one of cardboard,÷b÷e under the paper to cushion the pin from the hard metal s urface. The mans-÷b÷e facturers tell mj that I had an early machine for revie w, and that current÷b÷e machines h|c

P713 CJEFAX 713 Sun 22 Dec 16:44/52 |B220A210|a19$.PLOTMAT|i24BBBC332k|l44DE Aavj damping on the pin lift solenoid to alleviate this problem.÷b÷e If an attempt is made to draw a line off the e doe of the paper, the pen÷b÷e stops a t the edge, but remembers where it should be, so that on÷b÷e re-inte ring the active area, the line comes ba ck in as if it had been÷b÷e drawn from the point outside, just like the s creen does. There can bj a÷b÷e consi disable delay while it tries to draw 'out of bounds'. It appears÷b÷e that the part of the software which calculat es the steps for the motors÷b÷e ism 't informed, or doesn't realise, when it is out of bounds, and keeps÷b÷e ca lculating until it reaches its destin ation. Without knowing exactly÷b÷e w hat is going on, it is impossible to s ay if this problem is avoidable,÷b÷e but I feel that it should bj.÷b÷e I f enabled, a colour change called fo|c

P713 CJJFAX 713 Sun 22 Dec 16:40/28 |B220B210|a19$.PLOTMAT|i24BBBC332k|l4513 Fr bz a GCOL command, will stop the÷b÷e plotting, and prompt on screen to chan ge the pen, and show which colour÷b÷e the program wants to plot in. Six pe ns are provided - Red, Green, Blue,÷b÷ j Magenta, Brown, and Black, and spar es are available, albeit at what seems÷b ÷e the rather expensive price of |—9.7 8 per pack of six. (Packs with just Red ÷b÷e or just Black pens, and Ball-Poin t packs are also available.)÷b÷e÷b÷e Page 2 ÷b÷e÷b÷ e÷b÷e÷b÷e÷b÷e The Linear Graphics PLOT MATE A Cje fax review÷b÷e÷b÷e The package come s with an A5 size handbook in a ring-bin dir, with clear÷b÷e explanations, and examples in both BASIC and LOGO. Use of the software is÷b÷e not limited to hi gh level languages, and instructions fo r accessing the÷b÷e various face|c

P713 CEEFAX 713 Sun 22 Dec 16:42/41 |B220C210|a19$.PLOTMAT|i24BBBC332k|l4548 7lites from machine code are also clearl y explained.÷b÷e The disk has a number of very impressive demonstrat ion programs,÷b÷e including a high res olution map of Great Britain, which inc idently takes÷b÷e 18 seconds to pl ot on the screen, and just over two menu res to both the÷b÷e screen and paper; also 3D-histograms, and one that shows all the special÷b÷e facilities availa ble.÷b÷e As the microprocessor in t hj Beeb is doing all the calculations to move÷b÷e the plotter arm, it's inters ups flag is set while any movements are taking÷b÷e place so that these can be as fast and as smooth as possible, w ith the÷b÷e result that the clock lose s a lot of time, and any Events that h ave been÷b÷e set are likely to go unno riced. This shouldn't bj a problem howe vet, to a÷b÷e program that is creating a static drawing. Anothjt point to|c

P713 CEEFAX 713 Sun 22 Dec 16:46/24 |B220D210|a19$.PLOTMAT|i24BBBC332k|l457D C watch for is÷b÷e that when printing text, there is no automatic wrap-around , so if the text÷b÷e goes off the sigh t of the paper, any that follows is lost until the next÷b÷e carriage-return. This is reasonable, as odd characters on the lift of the÷b÷e paper are under irable. In BASIC the 'WIDTH' pseudo-var iable can bj set to÷b÷e help with this problem.÷b÷e If this plotter is used in schools with small childr en, close÷b÷e supervision will bj n ecessary, as care needs to bj taken wi th what is,÷b÷e after all, a piece of precision engineering. There is a smal l (10mm) gap÷b÷e where the travelling arm emerges from the case, that could i nvite them to÷b÷e deposit pencils and the like into the innards. It is also p ossible to put÷b÷e a finger in and g et it caught bz the moving arm. The ste pper motors are÷b÷e quite weak how|c

P713 CJJFAX 713 Sun 22 Dec 1v:41/02 |B220E210|a19$.PLOTMAT|i24BBBC332k|l45B2 Fever, so no harm would come to them - but they might bj a÷b÷e little start led at the thought of a crushed pinky! The worst that can in÷b÷e fact happj n is that the motor would stop, and the software would lose÷b÷e track of w here the arm was, so necessitating a re- initialisation.÷b÷e An extra unit is available, called the 'Intermate', w hich frees the÷b÷e computer's proces sot from all the calculations, and allow s the commands to÷b÷e bj sent via the printer port (serial OR parallel). Extra EPROMS are÷b÷e available for t his to allow emulation of the Hewlett Pa ckard and 'Sweet P'÷b÷e plotters, thu s enabling owners of IBM PC's to use t his plotter with the÷b÷e minimum of hassle. The PLOTMATE A4M has just been released which÷b÷e incorporates the electronics of the INTERMATE, and is much cheaper than÷b÷e buying |c

P713 CJJFAX 713 Sun 22 Dec 16:42/11 |B220F210|b19$.PLOTMAT|j24BBBC332k|l45E8 4thj two units separately.÷b÷e In conclusion, with the exception of a few minor problems which can bj÷b÷e expect ed in any new piece of equipment, the s is a very useful accessory÷b÷e for a nyonj who prepares statistical reports, or wants multi-coloured or÷b÷e bert er graphics than a matrix printer can p rovide. For the individual÷b÷e hon j usjt it is probably a luxury, but it would bj invaluable in schools÷b÷e or other institutions where a lot o f people using computers may÷b÷e o ccasionally want the facilities that i t can provide. That said, it is÷b÷e very good value for money, and being sof tware controlled, more facilities÷b÷e will undoubtedly appear in the future. Already Linear Graphics can supply÷b÷e mapping, circuit design, chart design, and CAD packages - contact them at÷b÷e the address below for more detail|c