It’s far easier to use the #Open_Serial instruction which automatically populates a CCB table and calls this instruction.  For anything other than the default port, you’ll need to say:
   #Open_Serial Port( 25x ) User( … )

Applies the Communications Control Block at address nnnn in NVEM page 0 to the serial port at address pp.

This differs from the same instruction without the leading ‘a’ in that it explicitly nominates a serial port address (pp) rather than the default serial port.

Note that SPLat will not switch away from its native SPLatLink protocol in the first 10 seconds after a reset. This is done to make sure you can always gain control of a controller with SPLat/PC.

Dialect exclusions: Not available in dialects before 29

Can only exist on boards that have an uncommitted serial port other than the programming port.

See also ComTestStartTimer Communication Control Block elements