Si538x/4x/9x General Troubleshooting Guidelines: I’ve set up my timing chip but I do not see an output

1. Make sure there is power to each of the VDDOs. If using a Silicon Labs EVB this means you can go to the EVB GUI of CBPro to the Regulators Tab and make sure the regulators are all turned on.  Or you can turn them on and keep them always on using the jumper pins on the EVB located near each of the outputs.  See KB Article about EVB Outputs for the Si534x/9x/8x https://www.silabs.com/community/timing/knowledge-base.entry.html/2018/11/08/si534x_9x_8x_evbout-HMKe

2. Check the OEb pin on the chip. The OEb pin provides a convenient method of disabling or enabling the output drivers. When the OEb pin is held high all outputs will be disabled. When the pin is not driven, the device defaults to all outputs on. The OEb pins have an internal pull down. For the Si5397 and Si5347 devices when using the OE1b it is recommended to use an external pull down to ensure the outputs are on, or a pull up to ensure they are off and not leave this pin floating. The OE0b pin has an internal pull down, but this OE1b pin does not in this case only. Outputs in the enabled state can be individually disabled through register control. Please NOTE: If the OEb pin is high, then register control is disabled, and all outputs will be disabled.

3. Check the OUTx_PDN Registers and make sure they are NOT powered down.  Also check OUT_PDN_ALL, and PDN. These are all documented in the reference manuals for the specific parts. 

4. Check the Output Enable Registers (OUTx_OE). Verify that the outputs are enabled .  Also make sure OUTALL_DISABLE_LOW is set high, ensuring all outputs are not disabled.  This is a register to disable all outputs by clearing this bit.

5. Connect to CBPro and read the EVB GUI status registers? An output may not appear if something is wrong with the XAXB input. Verify there is no XAXB Error. If there is an Error, check the input going to the XAXB.  This may be what is causing the issue.

6. Is the chip programmed correctly?  Verify some registers that were written from the frequency plan on different pages to make sure there wasn’t an issue with programming the chip.  See AN926 for detailed examples on how to program these devices. It is possible the device was not programmed correctly which is causing the problem. https://www.silabs.com/documents/public/application-notes/an926-reading-writing-registers-spi-i2c.pdf