From: Marko Mäkelä (marko.makela_at_hut.fi)
Date: 2004-05-20 09:55:26
Hi Adrian,
> I have a home-made logic analyzer that I've used to analyze the IEC
> protocol.
Nice. I've been thinking of making a simple USB-based logic analyzer from
a FTDI FT245, but I haven't had time to do it yet.
> IIRC the C2N232 uses an at90s2313 at 8mhz? I believe I have a 2313 I can
> spare to build a cn232.
Excellent! I've made the code from December 11 available at
<URL:http://www.funet.fi/~msmakela/c2n232i.s>. The file has the wiring
information:
RESET 1. \/ 20 VCC
RxD PD0 2 19 PB7 CTS
TxD PD1 3 18 PB6 RTS
XTAL1 4 AT 17 PB5 RxD
XTAL2 5 90S 16 PB4 MOTOR (tape)
ATN PD2 6 2313 15 PB3 READ (tape)
CLK PD3 7 14 PB2 RESET (for serial bus; not used yet)
DATA PD4 8 13 PB1
SRQ PD5 9 12 PB0 SENSE (tape)
GND 10 11 PD6 WRITE (tape)
You'll need to wire the serial line (RxD, TxD, CTS, RTS) to a MAX232
to enable in-system programming with my CISP tool, and communications
when the system is running. See the schematic in
http://www.funet.fi/pub/cbm/crossplatform/transfer/C2N232/hardware/smdcr.zip
for a reference design. It's now also in PNG format, if you don't want to
or can't install Eagle.
> I don't really need the connections to the c64's tape port for this right?
Right.
> (except maybe vcc/gnd?).
I think you can get vcc elsewhere, but then it might be a good idea to add
some buffering to the serial bus lines. I've connected the bus directly to
the pins of the AT90S2313.
> If I do this, what should I try to sample?
First, you should check that SAVE and LOAD works. I have some notes on
how to do this somewhere, but I can't find them right now.
Sending a command to the drive, such as the equivalent of
OPEN1,8,15,"I":CLOSE1. It'd be very helpful if you could also
debug the code, because my family is keeping me busy these days.
> My analyzer only has 128k of ram which are good for some 128mS at
> about a sample per cycle. I could sample a little slower if necessary
> though.
I think that 128 ms is enough. If I remember correctly, the protocol
hangs already at the end of the first byte sent under ATN.
Marko
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