Software Clock-Divider

摘要

An A/D converter is to be sampled twice per second. A line-clock interrupt is available sixty times per second, but the sampling routine takes longer than a sixtieth of a second to run. The solution is a clock-interrupt handler that updates time-of-day, then if half a second has elapsed, allows interrupts (including itself) to be serviced while the sampling routine runs. Except for a small amount of set-up and exit code, everything can be written in Forth. (ERA citation 09:005582)