disabling interrupts under OS-9

[Bob Babcock]

There has been mention  in Info-C  of disabling  interrupts  when
executing  sections  of code which cannot  be safely interrupted.
Usually the sample code uses something like protect()/unprotect()
around  the critical  statements.   I would like to be able to do
this under OS-9/68K, but Microware does not provide the necessary
protect/unprotect  functions.   The  obvious  way of implementing
these by moving the appropriate  bits to the status register does
not work in user state because the machine  opcode is privileged,
and if the entire program is run in supervisor  state, OS-9 turns
off time slicing, which I don't want to do.

[The  reason  why I want  to do this is that  I have a background
process driven by a periodic interrupt reading A/D converters and
performing  various  display  and control  tasks.  The foreground
task needs  to be able to occasionally  read a different  channel
from the same converter  without  worrying  about a time slice or
periodic  interrupt  coming  at just  the wrong  time and messing
things up.]

Has anyone developed  a good solution to this problem?  Microware
suggests  that I write a trap handler, and put the critical  code
in it.  But that  almost  requires  that  I do some  68K assembly
language programming,  and I would rather avoid that if possible.
The other option is to set up "in use" flags to coordinate access
to the hardware, but that seems much more complicated  (there may
be more than two processes  competing for the same hardware,  and
also multiple devices to be shared).