For the Si504, is the initial command sequence required for every new write transaction, or only once at power up and/or after exiting sleep?
In the Si504 there is a default configuration in memory that starts up after Power-on reset, so no writes are required to startup the part. Before writing any command after either POR or exiting sleep, it is recommended to apply the initial/reset command.
Does the Si504 have a default configuration at power-up or does the device require configuration after power-up?
The Si504 has a default configuration in non-volatile memory that starts up after Power-on-Reset (POR), so no writes are required to startup the part. Note that the Si504 must go through power-on startup (default configuration) before any commanded changes can be made.
How far can the Si504 output frequency slew in glitch-less fashion?
The minimum Si504 frequency step size is 2-25 or ~29.8 ppb. The slew range is 215 times this step size or ~ +/- 976 PPM so the Si504 can only slew in frequency +/- 976 PPM from the current programmed output frequency in glitch-less fashion. Please note: This range is relative from the current programmed output frequency and is not relative to any offset frequency. In other words, offsets cannot be compounded to get more than +/- 976 PPM range glitch-free.
No. The Si503 supports four frequencies using levels on the FS pin. Strong high is frequency 1, Weak high is frequency 2, Weak low is frequency 3 and Strong low is frequency 4. It does not support a tri-state as of today. Please contact Silicon Labs if this feature is of interest.