SN74LV393A: Request to suggest a hardware counter circuit that counts both positive and negative edges of a signal.

Mahima D

Part Number: SN74LV393A
Other Parts Discussed in Thread: TIDA-00580, SN74AHC123A, SN74LVC1G32, SN74LVC1G58

Tool/software:

Hi there,

I'm looking for a hardware counter circuit that counts both positive and negative edges of a signal. The circuit will be used with a "PEC11D" encoder. I'm currently using a decoder design recommended by Texas (TIDA-00580 reference design | TI.com), but I'm encountering an issue with the pulse count. The encoder I have has 30 detents for 15 pulses, so when I follow Texas's design for 2 detents, I only get one count. I'm seeking suggestions for an alternative approach that can handle both positive and negative edges. If you have any other better idea that would also be very helpful. Your input would be greatly appreciated.

Link: TIDA-00580 reference design | TI.com

Thank you

14 days ago

0 Clemens Ladisch 14 days ago

Guru 260930 points

Route the input to the /A and B inputs of two multivibrators (e.g., SN74AHC123A), and combine their outputs with an OR gate (e.g., SN74LVC1G32). This results in a positive pulse for each edge.

Alternatively, route the signal to both inputs of a Schmitt-trigger XOR gate (e.g., SN74LVC1G58), with one input delayed with an R-C filter. (This makes it harder to control the pulse length.)