3 ms·
The only pin numbering I ever perceived as unintuitive is on PLCC packages where pin 1 is in the middle of one of the 4 sides. Especially since there's still a
by eqvinox 7y ago
The only pin numbering I ever perceived as unintuitive is on PLCC packages where pin 1 is in the middle of one of the 4 sides. Especially since there's still a marker dot in one of the corners generally.
Luckily, PLCCs are rare these days.
Example: https://www.zilog.com/manage_directlink.php?filepath=docs/z80/ps0180&extn=.pdf https://www.zilog.com/manage_directlink.php?filepath=docs/z8...
(Note that the orientation on the PLCC package is indicated by one of the corners being different, yet that's not where pin 1 is.)
- neltnerb 7y agoYeah, I've seen those. Do you have any idea why they did that? I had twenty or thirty on a recent board and they took so much extra work to double check because they didn't follow convention. I probably read that pinout in disbelief for an hour before I called them to check. I think that's why people number them the counterclockwise way, if they didn't they'd get furious engineers calling them and yelling (I didn't yell, I was just very confused) that they aren't following the standard. There are so many ways to make a mistake in a circuit board already, once someone decided on a numbering scheme momentum probably just kept it going to be honest. Why would you change it when there is no functional difference and it makes mistakes less likely?
- eqvinox 7y ago> Do you have any idea why they did that? No, not the slightest clue. If you find an answer, I'm interested too...
- neltnerb 7y agoAll I can find is the definition, which states that pin one is in the middle of the top at least in the 44 pin package. http://www.interfacebus.com/ic-package-plcc-dimension-outline-drawing.html http://www.interfacebus.com/ic-package-plcc-dimension-outlin... No idea on the history though, hopefully someone can enlighten us, Google did not.