Requirements

The timing of the bus traffic is critical. In the current system, the high-level software handles the parity settings and so forth by issuing calls from the task level. This is somewhat unreliable, as the task may be preempted and the bus transaction will time out. It is therefore necessary that the device driver handle this situation using the kernel facilities and interrupts. See the timing diagrams in Figure 2 of ref.[3] for details of the timing and protocol to be implemented.

The driver must:

• Work on from one to three ports of an MVME167 single-board computer simultaneously.
• Allow various baud rates to be set. The standard baud rate is 57.6K baud.
• Not use busy-waiting to handle character transmission and reception.