> doc.SerialSpt

Title: Serial support module
Author: David De Vorchik
History:
        25-Mar-91 DDV Created.


Serial Device Support
---------------------

This module provides the backwards compatibility section of the new device
drivers, the module intercepts the related OS_Byte and OS_SerialOp calls and
then converts them to new improved whiter than white calls to the actual
device driver.

This has been done for two main reasons:

  i) To keep backwards compatibility,
 ii) To aid future writiers of serial device drivers.

The backwards compatibility has been kept as much as possible, although as
under RISC OS 2.00 some areas are not fully handled, ie. using a certain
sequence of OS_Bytes and OS_SerialOps can cause the system to get out of
line.

The seperation was also performed to aid future developers of serial devier
drivers, they need only worry about talking to the actual hardware rather
than having to implement the code that convinces the machine that it is
really a BBC model 'B' which part of the support module actually does.

Once installed the module hangs on SerialV and ByteV, through these are
passed the calls to OS_SerialOp and OS_Byte.  The kernel in RO2.50 will
already change the calls to OS_Byte into suitable OS_SerialOps making the
task a bit easier, although not all are handled.

