Re: Two projects
Date: 1998-03-23 20:46:05

Hallo Olaf,

Aan 20-03-98 21:45, in bericht <>, 
Olaf Seibert <> schreef:

> Yes, in the PETs,


>  and basically also in the 64,


>  most signals (but I
> don't think ALL signals) go OUT though an inverter but they come IN
> without an inverter.

PETs NO again, 1541 YES.

>  I'm sure that's needed somehow electrically. To

NPN transistors behave better and quicker for some reasons then PNPs. It has 
something to do with quantum mechanics I was told so don't ask me further :-)

> compensate for that, the software inverts the signals again. On top of
> that, some signal names have another inversion in them: NRFD, NDAC...
> (NOT ready for data, NOT data accepted) All this can be very confusing.

The word NOT has nothing to do with the active level of the signal. The 6502 
has a active (L) RESET input.  The 8255 has an active (H) input line. 

> While we're dreaming: not only PCs have ISA slots, so if possible don't
> do anything that depends on PCs unnecessarily.

A bus is a bus is a bus. At this moment I need addresslines, a databus, a read- 
and a write-line and a line to slowdown the guest system. Except the last line 
the others can be found on every bus I know. The ZX Spectrum does NOT have the 
slowdown line and cannot be used for this purpose. Andre has a Atari and he 
could tell us if this machine has such a line at his slot. 
Even if the machine does not have this line, you can create one. The only 
reason I don't mention this in the first place is that I want to keep the 
machines as original as possible. In this way you make it also interesting for 
people who don't want anybody to touch their precious computer with a solder 

Groetjes, Ruud

Archive generated by hypermail 2.1.1.