NS32FX211 Datasheet, PDF (10/12 Pages) National Semiconductor (TI) – Microprocessor Compatible Real Time C

Functional Description (Continued)
2) Read out all the time registers required The registers
may be read out in any order simplifying software require-
ments
3) Read the lowest order register and compare it with the
value stored previously in step 1 If it is still the same then
all time data is good If it has changed then store the new
value and go back to step 2
In general the rule is that the first and last reads must both
be of the lowest order time register These two values can
then be compared to ensure that no change has occurred
This technique works because for any higher order time reg-
ister to change all the lower order registers must also
change If the lowest order register does not change then
no higher order register has changed either
TL F 11011 – 6
FIGURE A-1 Time Delay from Clock Setting Pulses to Interrupt is Constant
TL F 11011 – 7
FIGURE A-2 Interrupt Timer Synchronized with Clock Setting Pulses
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