Jim, The /PAL input to the 8701 is either jumpered to ground or open. There are two configuration lines on the clock chip that you need to alternatively pull to ground to make the selection, i.e. input A grounded for PAL OR input B grounded for NTSC. If they are not grounded, they can be left floating or pulled high. On the new PCB the /PAL input is pulled high via a 10K resistor and then runs to the inverter input and input A. The inverter output goes to input B. You alternate pulling two lines low with one input. If you use a transistor then you would also need 2nd resistor to limit base current and a third to pull the collector high. Or you could use a mostfet and maybe not need the second resistor. But still you would still have an SOT23 transistor and two resistors to fit in a tight space. The cost difference between an inverter gate and a transistor + another resistor is negligible when building a few of these. If you wanted to build a million it would be a different story. I also did not want to go smaller than 0603 chip parts so as to not make it impossible for others to construct themselves at home. Jeff Birt From: Jim Brain <brain_at_jbrain.com> Sent: Saturday, July 11, 2020 8:10 PM To: cbm-hackers_at_musoftware.de Subject: Re: New small sized MOS8701 replacement Not that sot23 inverter is not a good solution, but I would think a transistor and resistor would also implement a NOT gate needed. It's not like the signal will be switched a low, so a weak high via pullup and a pull to ground via PNP should do the trick, no? Jim -- Jim Brain brain_at_jbrain.com <mailto:brain_at_jbrain.com> www.jbrain.com <http://www.jbrain.com>Received on 2020-07-12 05:00:03
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