According to my read of the datasheet, POL needs to be high in order for blanking to extinguish all cathodes. That also would explain why sending a '0' to the HV5530 will cause a cathode to illuminate. So, if you have POL low you will be attempting to turn-on all cathodes at the same time. The power supply is probably current-limited so it would prevent all cathodes from actually glowing.
Regarding the CLK, the inversion of every-other clk-input is way to guarantee hold-time is satisfied when shift registers are cascaded, at the expense of setup time. Basically, the sending device transmits on the falling-edge of clk, and the receiving device samples on the rising-edge (because of the added inverter). You have a guaranteed hold-margin of 1/2 clk cycle. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/61bc002d-849d-4a0d-b979-98aa16be3617%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
