Other Parts Discussed in Thread: TPS54531, CD4511B, SN74LVC2G32, SN74LVC1G14, SN74AC32
The CD40147's truth table is negative logic where 0 is high and 1 is low (Why is baffling, but that's another question.) I can accept the negative logic for the INPUTS at face value but am confused with the OUTPUTS.
If a 1 (low) is put on the 9 pin it says the DCBA output is 1 0 0 1 or (with negative logic) LO HI HI LO. But if you feed LO HI HI LO to a 4511 BCD to 7-segmwnt decoder it will output the digit 6, not the digit 9. Do I need inverters between the 40147's BCD outputs and the 4511's BCD inputs? Seems silly! Or per chance is the OUTPUT truth table of the 40147 actually positive logic? In which case a 1 (low) on the 9 pin would output HI LO LO HI and the 4511 would display the digit 9. Can anyone help clear this up?