Not a bad little trick, and by using it, you can get at all the legal calls within the
CBIOS. The only snag is that I’m not sure it’s entirely legal. I’ll bet some person
will decide that it shouldn’t be used within CP/M.
Still thats all about disks for this time, except to remark that this issue of
INMC has been prepared using the new DISKPEN with all its enhancements, and of course,
the whole issue was saved on a couple of disks.
SCREEN CONTROL UNIT REVIEW
This is a review of the Screen Control Unit produced by:
R. W. Electronics, 27 The Vineries, Acocks Green, Birmingham, B27 6SB. The kit costs
27.00 inc. P&P and VAT.
This control unit provides 5 functions/nbsp;:- reset, display on (normal), display off
(blanked), white on black (normal), and black on white (reverse video). It is
constructed on a single sided 8″ X 5.5″ fibreglass pcb that plugs into a NASBUS and
has a wire connection to an existing Nascom IC socket.
The sample kit provided for review took under 2 hours to build on the well prepared
board, the legends being very clear and informative. Over half an hour was spend in
inserting the wire links required since the board is single sided.
No problems were encountered in building the kit. In fact this is one of the best
presented kits our reviewer has seen. The only hiccup occured because the kit was
first configured for a N1 (someone else can’t read simple instructions?) and could not
be tested on the N2 available. The kit is not intended to be changable between N1 and
N2 but with some careful soldering this was accomplished.
Anyone who is thinking of purchasing this kit should also acquire another edge
connector socket since there is not one in the kit.
Testing of the unit presented no problems (it worked first time) although the
suggested memory address for the unit (it uses a memory mapped port to control it)
seemed a little strange. The handbook suggests using address D000H (selected by wire
links on the board) but 0800H would seem a better alternative since this is not used
by any known software and provides a record of the last code sent to the unit in the
first location of screen RAM.
In summary, this would be a very good first project for someone who purchased a built
NASCOM and now wants to learn a little about assembling kits. The unit offers only VDU
on – off, and screen inverse, and as such would seem to be somewhat overpriced.
Perhaps a NASBUS socket could be provided in the price since it would appear that all
other Nascom hardware suppliers provide a socket in with their kits. However, if you
consider the time and effort involved in going it alone with a ‘DIY’ job, this unit
would probably work out cheaper.