Quote:
Originally Posted by ScottishColin
Yes - they're linked and I get continuity all the way to UC5/18 from pin 4 for example.
I'm interested why they're called jumpers though.
Any views on the higher voltages on pins 3&4 of the second cassette port?
Edit: Just realised there are actually THREE groups of those cassette jumper pads on the diagram.
|
Jumper links were originally just a soldered hard-wired link on the PCB, that jumped across tracks - Not only for (re)configuration of the connections:
https://www.harwin.com/connectors-ha...horting-links/
But if done with a 0.1" (or sometimes 2mm on smaller more recent boards) spacing, then they did allow the use of removable shorting-links that became widespread on later PC's and FDD's / HDD's etc.
The BBC computer also had some soldered ones, as well as lots of removable shorting links on headers (although on the Acorn System 1 etc they had originally often had provision for (non 0.1") wire-links which also had a PCB track across. So you didn't need to fit the link, unless track had been cut, to reconfigure and then wanted to change again)
On the PET cassette interface, they do seem just to make it more confusing to follow the schematic, as if you changed which port-lines controlled the interface, then you'd have to have a different version of the Kernal etc. ROM.
So I can see why they would have been permanently soldered-in. (Although I don't recall Commodore ever having removable links, and I'm sure the first IBM PC's just had DIP-switches for memory-size setting and didn't have any links)