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From: H Zoli
Date: 2000-07-04
Subject: HW Q

Hello All,

Some time ago I was on this list, now I subscribed again.
I had also owned a +/4 before. I dont have any computers at the time except a Sony PSX.

I've got some HW questions.

I'm planning to build a simple car/engine tester.
This means measuring freq of some signals
(crankshaft rpm and actual speed of car), and there would be simple counting (ignition timing) too.

I came to 3 solutions:
(first 2 are offtopic, sorry. someone may be interested..)

- PC/AT 286: cheap, requires no power supply in the car
(has own battery), sensors can be built of opto-gates of a mouse. Mouse movement can be easily read via BIOS routine calls, from machine code or pascal either. Can store much more data than following 8-bit versions. Graphs can be drawn more easier since the higher level programming.

- Z80: a cheap and simple architecture is a Sp*ctrum,
w/ a CTC hooked up on its expansion slot. (CTC=
Counter and Timer Circuit). It can be programmed to count internal clock or ext. trig., then it requests an interrupt, which can be a vectored one for example.
A ZX-Sp*ctrum has built-in voltage stabilizer, it requires anything between +7V..+11V DC, this is OK in a car.
Display can be a small 12V TV-set.

- third idea (and this is the "ontopic" part): C64 or plus4.
Plus/4 has a great advantage compared to the spectrum:
the MONITOR command which I used a lot. (on the other hand I prefer Z80 or 80286 coding /I am very sorry/...)
This allows me to correct the code instantly, parking on the street, between two test-accelerations - in the car..
But I need to know a few HW specifications, could someone help me? thanks in advance.

1: what power supply does a c64 or plus/4 need?
is it a stabilized voltage level or does the computer have internal stabilizer? I remember it gets AC from the supply. Is it correct?

2: are there (I suppose yes (sound IC..)) some timer/
counter circuits?

3: if yes, how many channels does it have? I need two (3 is better) counters w/ external trigger signal possibility, and at least one programmable timer channel.
what is the minimal time interval of the timer, and how many bits do they (timer/counter) count on?
I think timers can be different on a c64 and a +/4,
since their sound capabilities are different too.
What are the details?

4: are these trigger/clk lines available from the expansion slot or via user port? are they standard TTL level?

5: can I program the timer/counter to generate interrupts, and can these interrupts be vectored ones?
If yes, only the measuring code would be in assembly,
other math+graph could be done in basic, getting the actual numbers w/ a PEEK(). What interrupt modes are there?

At last: do you plus/4'ers have an existing method to connect a C= to a PC and transfer data
(via serial port or any other port) ?

thanks again and sorry for bothering ya w/ offtopic machines :-)

z.

PS. spectrum has more resources on the net worldwide,
but commodores have more support in Hungary.
It is also easier to obtain a C= than a ZX.