PsiFS: SWI Calls

The changes of interest are specified by setting bits in the mask passed in R1:

Bit	Changes reported when set
0	mode of operation
1	serial block driver configuration
2 ~ 3	must be 0
4	number of bytes or frames transmitted or received
5 ~ 7	must be 0
8	remote link configuration
9	remote link connection status
10	remote drive details
11	must be 0
12	asynchronous operation completed
13	asynchronous operation status
14 ~ 15	must be 0
16	printer mirror configuration
17 ~ 19	must be 0
20	file transfer intercept status
21 ~ 31	must be 0

The returned pollword is suitable for passing to Wimp_Poll. It should also be passed to PsiFS_Unregister to unregister the client. PsiFS will set the pollword to a non-zero value whenever there is any relevant change in status. It is the responsibility of the client task to clear the pollword back to zero and to discover what has changed.

The recommended sequence of events is:

1. Wait for the pollword to become non-zero, e.g. by calling Wimp_Poll.
2. Clear the pollword back to zero.
3. Check for changes to any options of interest by calling PsiFS_Get and PsiFS_InterceptPoll.