Okay, the F-RAM chip is in place and working. Taking all delays out of the code I can get a sector (517 bytes) of the MMC onto the F-RAM in about 13.5ms (MMC > PIC > I2C). That's much faster than the old I2C. It's nice not having to stop and write the buffer page!

I'm still looking for a faster way to move the I2C data line, so I'm writing my own I2C handler routines. My whole program cycle has to fit into 16.67ms. It doesn't look like I'll be able to load the I2C with sample data then move it to the MMC in this window unless I can get the program cycle, minus the data captures, down to about 6ms. It's going to be close.