On Fri, 22 Feb 2002, Daniele Gratteri wrote:
> When the tape is connected, all the values of the cassette connector
> (measured on the bottom of the board) are near 0V or 5V. If I send a LOAD or
> SAVE command, the one I found to be the READ is around 2V, another one is
> over 6V (!). But maybe it is another signal.
The 6 volts sounds like the power supply of the motor.
> Do you know what are the READ and WRITE pins? I think I made mistakes...
Aren't the pin numbers printed (or embossed) on the outside of the
connector? There should be tiny numbers next to the holes. According to
http://www.funet.fi/pub/cbm/schematics/computers/plus4/p4-left.jpg and
http://www.funet.fi/pub/cbm/schematics/computers/plus4/connectors-2.jpg
the plus/4 cassette connector pinout is like this:
1=ground
2=+5V
3=motor
4=read
5=write
6=sense
7=ground
BTW, when I tested the C2N232 with the plus/4, I removed the cord from the
inside of a plus/4 tape drive and soldered the tiny connectors to my
circuit board. I think that it could be easier for you to measure these
voltages from the inside of the tape drive, as the connector there uses
wider spacing.
On Sat, 23 Feb 2002, Richard Atkinson wrote:
> If those capacitors are doing what I think they are doing, they are there
> to improve the start-up time. If this isn't important in your circuit,
> then by all means leave them out.
The 33 pF capacitors are connected from XTAL1 to ground and XTAL2 to
ground. The crystal is connected between XTAL1 and XTAL2. BTW, in my
first microcontroller project (a 8-channel thermometer with a 16×2 LCD,
which I scrapped to make the first C2N232 prototype), I made the very same
mistake Konrad mentioned: I had nF-range capacitors in the crystal
circuit, and the crystal didn't want to oscillate.
I'll test the cost-reduced C2N232 with more computers. The first
prototype definitely seemed to need the CASS READ pull-up when it was
connected to the VIC-20. But I've changed the software a lot since
then, without measuring the signals with an oscilloscope.
Marko
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