17 Aug
1997
17 Aug
'97
8:57 p.m.
I bought: A TI-99/4A (Not as lucky as Roger M - I
paid L12 with no
joysticks, manuals or cartridges, but I did get the UHF thingy)
Nice!!!....
But the real find: A British Telecom Microscribe for L1
Very nice...
This object is a solidly built sub-notebook (about 7 in square by 1
thick) with a dinky keyboard and a palmtop-sized LCD. It has 32K of RAM
and 16K of ROM, and the processor is an Hitachi HD63A03XP single chip
microcomputer.
Is that the only processor? It sounds as though it might be distantly
related to a Thorn-EMI machine called a Liberator which had a 63-something
for I/O and a Z80 running a CP/M like OS (or at least, that what I think
is inside it - the ROM is (C) Digital Research, and running strings on a
ROM image turns up some interesting stuff)
THE LCD looks as if it might be 200 or 256 by 64 pixels (40 characters
by 8 lines?) - I haven't powered it up yet because (a) the NiCd battery
is flat and (b) I have yet to work out what voltage to feed it (3.5mm
jack with tip negative). All I know is that it must be smoothed DC,
since there is a diode but no smoothing capacitor in the input stage.
Not so. A lot of machines use the NiCd as the smoothing component. HP
certainly did in just about all of their more recent NiCd calculators (the
ones that use the 8V 50mA AC charger).
Some, like the Epson HX20 even used the fact that the voltage across the
NiCd would go above 5V to limit the supply voltage to the chips. The HX20
had no other power regulator. (Yes, there is a zener diode across the
lines, but that's just protection if the NiCd goes O/C)
If you have an adjustable PSU, apply about 5V, and then crank it up
towards 9V (I'd guess that's what it takes), monitor the 5V line and stop
if it rises above (say) 5.5V. See what current flows - it should be
arround 50mA.
Philip.
-tony