From: Jim Brain (brain_at_jbrain.com)
Date: 2004-10-23 22:42:03
Just a short note... Hársfalvi is my lastname... so, just in case you
intended to call me by my firstname, you should call me "Levente" ;-).
Many apologies. The last_name first_name thing is hard to discern from
context.
> The 10 cycles delay is introduced by the 10k resistor. I used it
> mainly for safety reasons and compatibility (the 1351 had 5.1k, but
> due to the 5717's outputs having greater resistance than the PIC16c84
> outputs, I raised it to 10k to meet similar delay in overall). Though,
> I haven't investigated this further. In theory, you could completely
> omit the resistor; after that move, the minimum value (read from the
> SID registers) is a function of
I tried that last night, but if the resistance is < 3k, the
uController's ability to source is more powerful than the SID's ability
to sink, so no falling edge is seen, so the unit does not work.
However, at 3k, I can get down to "4".
> Actually, you could use the Atmega8's internal RC oscillator (in case
> you're experimenting with a 'mega8 ).
I have one here, but was using a 16 for initial tests. However, I'll
try the 8 I have.
> The biggest problem -- if I'm correct -- won't be the protocol itself,
> but the interference with keyboard activity. ...But I may as well be
> wrong in this.
My protocol idea assumes you don't scan the keyboard rows during the
time you request raw data.
Jim
--
Jim Brain, Brain Innovations
brain@jbrain.com http://www.jbrain.com
Dabbling in WWW, Embedded Systems, Old CBM computers, and Good Times!
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