It's more like 6ms.

There's the 2-byte buffer, and you can receive all but the last bit of the 3rd byte before it overflows. But in order to get that time, you'll have to disable the RCIE bit. Otherwise, since you are using ASM interrupts, it'll trigger the handler and interrupt the Pulsout timing on every byte received.

But anyway, the servo pulses should only be sent every 20ms (50hz). If you have continuous data coming in, and you're sending a pulse every time you get a new word ... the servo's not going to like it.
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