Please confirm error in 74HC245 library symbol

[dchisholm]

I believe I have found an error in the KiCAD 6.0.5 library symbol for the 74HC245 bus transceiver. Before I report an error or draft a corrected version of the symbol, I’d appreciate somebody confirming that the error is still present in the current (8.0.1) version of KiCAD.

The error is the presence of a stylized hysteresis curve in the KiCAD symbol, generally used to indicate Schmitt-trigger logic inputs. The 74HC245 does NOT implement input hysteresis, so the symbol in the KiCAD version 6.0 library is misleading.

(To confuse matters . . . . the 74LS245 version of this part DOES have input hysteresis. Why somebody would omit this feature from a bus transceiver’s input is beyond my understanding, but it has apparently been the norm for over 40 years. The 74HC7541 is a similar part which DOES include input hysteresis, though it is not directly interchangeable with the 74HC245.)

As previously mentioned, will somebody please check and see if the KiCAD 8.0 library symbol for the 74HC245 displays the hysteresis notation?

Thanks,
Dale

[ML9104]

Can’t comment on V8, but in V7 it’s the same as you see.
Why?
Because the 74HC245 symbol is derived from the 74LS245 symbol (= same graphic).
That’s the lazy way.

I strongly suggest that you create personalized libraries. More info in the FAQ section.

[paulvdh]

In V8 the HC245 is still derived from the 74ls245, including the schmitt trigger symbol in the center.