PCA9615 / PCA9616 Termination Resistors

[rasid_pac]

When I use the recommended termination resistors in the datasheet of PCA9616 (R1 = 600 Ohm and R2 = 120 Ohm) with CAT5 cable, the system in the attached picture doesn't work (PIDET and READY lines remain high). However, if I change the resistors on the master side to R1 = 390 Ohm and R2 = 100 Ohm as in Sparkfun's design, the communication works and PIDET and READY go low. I haven't tested other resistor combinations yet but will update here as I do.

Does anybody have any input on this?

Thanks

[guoweisun]

What's the value of VDD?

[rasid_pac]

It is 5V for VDDB and 3.3V for VDDA. I found the problem though. There was some miswiring in the termination at the slave end of the bus.

[guoweisun]

You can try R1=600ohm,R2=100ohm on both sides.

[rasid_pac]

Yes, thank you but no need anymore. 600 and 120 work just fine after fixing the wiring.