Following from this comment
Here's the Spin2 Interpreter, so far:
Attachment not found.
This interpreter is for the built-in 17-bit address space (128KB), but can easily be changed to 32-bit XMM. I started out on the 32-bit addressing path, but figured it was more practical, at first, to make a native 17-bit version, as an external SDRAM can easily be managed by Spin code for huge data.
This interpreter leaves the first $150+ longs in the cog free for in-line assembly code and terminate-stay-resident type applications which can run concurrently with the interpreter via hardware multi-tasking.....
and seeing this new Si504 Clock device (32Khz ~ 100MHz) :
claims price " begins at $0.44 /10k", and it looks simple to talk to : 1 pin, but edge-change-modulated, so would need PASM, and it directly accepts a real number, and an (optional) offset integer.
Some command code examples :
NewFreq [0x0C] + 4 Bytes (floating point 32-bit IEEE-754 number in Hz, MSB first)
OffsetFreq [0x3A] + 2 Bytes (signed integer MSB first) Offset Frequency in increments of 29.8 ppb (or 2^-25).
A small portion of that first $150+ longs in the cog free for in-line assembly code
could load the Frequency.
This little part would complement the PLL, and it looks like the Offset mode allows a digital trim to lock to something like a GPS 1pps.
Depending on the 'real' price of the Si504, this could be a great part to place on any Prop 2 breakout board.