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Sync polarity behavior

Category: Datasheet/Specs
Product Number: HMC7043


I'm designing a clock distribution system with an HMC7043, at the moment I'm trying to understand how the synchronization procedure works. In particular I'm sending a sysref clock to the RFsync input and this has to trigger the synchronization, but I'm not able to fully understand what is the effect of the Sync polarity control bit 0x005B[3].

What I'm doing is sending a continuous sysref signal at 1 MHz to the RFsync input and then I interrupt it, I'd expect that the last rising or lowering edge would trigger the synchronization depending on how the sync polarity bit is chosen. But then if I set the Sync polarity to 0 I see some synchronization happen (I think after the last falling edge) and if I set the bit to 1 I don't see it (while i'd expect it to sync after the last rising edge). Please explain me where I am doing a mistake in this reasoning.

The main clock is at 1 GHz and I set the sysref timer to be 2000 (so its period is 500kHz).

The yellow signal is the sysref clock connected to the RFsync input and the orange signal is the clock output of the HCM7043, the blue one is just a trigger.

I'm using LVDS protocol and everything is DC coupled.

SYNC polarity 1:

SYNC polarity: 0

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