Specifications

Device Driver Entry Points
Timeout Handling Routine
Input
Location Contents
R3 Contents of R3 when the last invocation of
WFIKPCH or WFIRLCH took place
R4 Contents of R4 when the last invocation of
WFIKPCH or WFIRLCH took place
R5 Address of UCB of the device
UCB$L_STS UCB$V_INT and UCB$V_TIM clear; UCB$V_
TIMOUT set
Exit
The timeout handling routine issues an RSB instruction to return to its caller.
Description
There are no outputs required from a timeout handling routine, but, depending
on the characteristics of the device, the timeout handling routine might cancel or
retry the current I/O request, send a message to the operator, or take some other
action.
Before calling a timeout handling routine, the operating system places the device
in a state in which no interrupt is expected (by clearing the bit UCB$V_INT in
field UCB$L_STS). If the requested interrupt occurs after this routine is called, it
will appear to be an unsolicited interrupt. Many drivers handle this situation by
disabling interrupts while the timeout handling routine executes.
4–20