By:
Masud-ul-Hasan
12
Clocking
Sources (contd.)
2. Event Counting:
•If C/T = 1 (in TMOD), counter
operation is selected and timer is clocked from external
source. Usually, external source supplies the timer with a pulse upon the
occurrence of an event. Timer counts those events.
•External
clock source comes through P3.4 (for Timer 0) and P3.5 (for Timer
1).
•Timer
registers are incremented in response to a 1-to-0 transition at the
external input.
•Number
of external events is determined in software by reading the timer
registers TLx/THx.
