Simple software RTC for time keeping

Keep time based on a tick interrupt

Variables holding the current time

variable seconds
variable minutes
variable hours

IRQ handler which will increment the time components based on a tick count of eight ticks per second

i: rtc-handler tick dup c@ 1+ dup #8 < if swap c! else
                  drop 0 swap c!
                  seconds dup c@ 1+ dup #60 < if swap c! else
                     drop 0 swap c!
                     minutes dup c@ 1+ dup #60 < if swap c! else
                        drop 0 swap c!
                        hours dup c@ 1+ dup #24 < if swap c! else
                           drop 0 swap c!
                        then
                     then
                  then
               then
               ;i

Print the time components

: rtc. base @ hours c@ . minutes c@ . seconds c@ . tick c@ . base ! ;

Reset the time components

: rtc-init 0 dup tick ! dup seconds ! dup minutes ! hours ! ;