Re: Real Time Clock on Cassette Write/Sense lines

On Sat, Feb 11, 2012 at 12:33:04AM -0600, Jim Brain wrote:
>Anyone see issues with wiring up a I2C-based (DS1307-type) RTC to the 
>cassette port with SCK on WRITE and SDA (data) on sense?  Looking at 
>schematics, READ is often hooked to CA1 or similar read-only pin, but 
>SENSE appears to be on a GPIO on all CBM machines I found.

Did you check all machines? IIRC, SENSE is an output-only on some 
computer (maybe the 264 series aka C16, C116, plus/4, or the 600/700 
series). Otherwise, I would have used SENSE in the custom protocol of 
the C2N232.

>My other idea is to put SCK on MOTOR and put SDA on the WRITE line, 
>which looks to be a GPIO.  But, I was afraid such constant cycling of 
>the MOTOR line with a datasette present might cause it's own issues.

Some fast disk copying program on the C64 (File hack'em or Fast hack'em) 
did cycle the MOTOR line when switching memory banks. It would emit a 
funny noise on the datassette, that's all. I guess that the authors did 
not have a datasette hooked up.

	Marko

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