1 Nov 2005 02:19
Re: advice needed
In a message dated 10/31/05 12:34:31 P.M. Eastern Standard Time, robert.gault@... writes: I can't remember any software using the monitor sensing line, but that doesn't mean much. The only problem might be that the PIA is configured for input on that line. You would need to change it to output. That means you will need to reconfigure any time the RESET button is pressed for the PIAs will be reset based on the ROM. Lets say that you burn a new ROM which makes $FF22 bit 3 an output. Now any software that wrote to $FF22 will probably have to be changed. None of the software using $FF22 expects bit 3 to be output so it may not keep bit 3 high. There is a fair chance that any software adjusting the video PMODE settings, or single bit sound could turn off your monitor. OK....I tried the break key and reset and they both turn that line into an input. This turns the monitor back on. This happens because there is a pull up resistor on the PIA line that pulls it up when the PIA signal becomes an input or "hi z" eventually causing the I2C data line to go high. My converter software uses that signal to drive the I2C data line that is high by default. By definition, all I2C devices release (go high Z) the data line when they don't need it so that other devices can be on the same line. This is called "wire anding". This also means that line has a pull up resistor to hold it high until another device needs it. The I2C software I have written for the unit releases(Continue reading)
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