16-bit variables for timers.

Erik is correct. I already use the auto reload feature of the timer to get it to repeat accurately at the 1 millisecond rate (or other rates if applicable in some applications). The issue of the disabling interrupts is totally like Erik said. If the mainline tries to poll a 16-bit timer counter variable it must access the variable in two separate 8 bit accesses. You don't want to try to guess what would happen to the mainline code if the timer interrupt happens just as one 8 bit fetch was completed but the 2nd was yet to be done.

Thanks
Michael Karas