I am using some logic chips by Texas Instruments, namely SN74HC02N, SN74HC04N, SN74HC32N and others.

When I connected them in my circuit, the SN74HC02N NOR-gate didn't work as expected, so I searched for a datasheet. It showed that the pin layout for the chip was reversed: It was Y, A, B instead of A, B, Y.

The other chips from the same family and manufacturer that I have are all A, B, Y. This is very counter-intuitive and doesn't make much sense.

Why does this one chip have a different pin layout?

Is there an alternative version that has a A, B, Y layout?

  • \$\begingroup\$ For sure NOR was backwards to OR et al,....;) it was not designed by the famous Polish IC designer who also did HP's calculator. ;) j/k .. even the CD4001 was different \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 11 '17 at 3:31

The NOR gate needs extra transistors, compared to NAND. In the days of single-layer metal, routing with that single layer may have required moving the "Y" output, so as to have the most compact IC layout and acceptable cost for the extra transistors.


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