cCall [pPortTransmitChar], <hPort, ch>
or eax, eax
jz error_handler
Called by the _VCOMM_TransmitCommChar service to send an "immediate" character to a port. The port driver must transmit the specified character before any characters in the transmit queue. Uses the C calling convention. Must be callable at interrupt time.
_PORTINFORMATION, PortOpen, _VCOMM_TransmitCommChar