XBee S1 maximum analog sample rate >1mS?

I’m running version 10ED firmware on my S1 XBee.

Maximum analog sample rate is documented to be 1mS, however, I’m seeing closer to 1.4-1.5mS when a 1mS interval is specified.

Is that right?

Are you talking about ADC sample?
If yes, then there may be a delay between the frames and you are noticing that delay.