What if you need to share multibyte data between 'task' and interrupt level
code, and you are not allowed to disable interrupts AT ALL.

Given:

The 2-byte variable 'shared_var'.

Problem 1: We want to guarantee that interrupt level can always get a
'reasonably current' and consistent value of the variable as set by task
level. (ie: value is never written by interrupt level code)

Problem 2: We want to guarantee that task level can always get a 'reasonably
current' and consistent value of the variable as set by interrupt level.
(ie: value is never written by task level code) (hint this is rather easy)

Problem 3: We want interrupt and task level both to be able to write to the
variable, and always get a 'reasonably current' and consistent value of the
variable. (ie: value is written by both task level and interrupt level code)
(this is rather tricky)

Criteria:

Minimum extra RAM locations used.
Minimum amount of code.

Have at it!

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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