Samsung S5PC100 User Manual page 602

S5PC100 USER'S MANUAL (REV1.0)
When Interrupt Manual Update (TCON[4]) is asserted off, after timer is expired, INTCNT (interrupt counter) is set
as 0. And interrupt is occurred at every TICK.
6 USAGE MODEL
Follow the restrictions given below:
•
TCLKB is equal to or slower than PCLKD1.
•
Set count value as big as possible (To improve resolution).
•
Prescaler, Divider Mux, TCLKB at TCFG must not be changed at run-time. If you want to change them, stop
timers in advance and then change.
6.1 INTERRUPT
There are four kinds of interrupt source in system timer. The first one is interrupt counter expired, and the other
three are SFR write status.
When you write value to TCON, TCNTB, and ICNTB SFR, the value may be not updated immediately to system
timer-internal counter, because sometimes system timer uses RTC or XXTI clock for counter. They are slower
than PCLK, operating clock of SFR. After those write status interrupts are asserted, SW can assure new value is
really updated at internal counter. SW must wait until that time.
Note) TCON and ICNTB-writing interrupt can be disabled by SFR. But TCNTB-writing can't be disabled. When
you write TCNTB SFR, that interrupt is always asserted.
If you don't want to assert interrupt, you can know update moment with continually reading INT_CSTAT[4:1]
(polling method). In that case, you can selectively enable or disable each source of interrupt. Please refer
TCFG[7:6] and INT_CSTAT[0].
6.2 COUNT VALUE UPDATE
Manual update (TCON[1] and TCON[4]) updates timer at that time. As described at 6.1, after write status interrupt
is occurred, you can assure that internal counter is really updated.
Interval mode (TCON[2] and TCON[5]) makes timers to update value in ICNTB and TCNTB automatically, after
timer counter is expired.
SYSTEM TIMER
7.2-5