Technical information

Serial Solutions NewBIOS Reference
Meaning._________
Service 4H is an extended initialise, providing more
functions than its sibling, service 0H. It is also easier to use
since it is not necessary for the programmer to build the
complex parameter byte written to the 16450, the service builds
it.
The baud rate parameter in CL is used to index a table of
divisors, one of which is written to the 16450 baud rate divisor
latch. The remaining parameters are translated into a byte which
is written to the 16450 line control register.
The 16450 line and modem status are returned.
Other Points.____________
The Baud rates available via the Serial Solutions service
are to be used with care as the higher ones will only work under
the most favourable conditions on a direct line and on a fast
machine.
Page 86 Chapter 5