On Fri, 24 Aug 2001, Eckhard Stolberg wrote:
> reading the timer only got me the interrupt register. Maybe I just
> mixed up the bits when I tried to transfer their address information
I think you did:
> read and clear interrupt flag: RS-, R/W, A2, A0 = 1
Ok.
> read interval timer: RS-, A4, A2, R/W, A0 = 1
read interval timer: RS-, R/W, A2 = 1: yes, but A0 = 0
(A3 enables/disables interrupt)
> read interval timer overflow: RS-, A4, A2, R/W = 1; A0 = 0
This is the same as the corrected "read interval timer" above.
I think you just mixed up A0 for reading the timer.
In summary, if you're reading the the timer or the timer interrupt flag,
the following applies:
RS- = 1
R/W = 1
A4 = don't care
A2 = 1
A1 = don't care
A0 chooses between reading the timer or the interrupt flag:
if (A0 = 0) => read timer
=> A3 controls the interrupt from the timer to IRQ-
A3 = 0 => disables interrupt
A3 = 1 => enables interrupt
if (A0 = 1) => read interrupt flag => A3 = don't care
=> A3 = don't care
-Chris
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