Samsung S5PC100, User Manual

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S5PC100 USER’S MANUAL (REV1.0) PULSE WIDTH MODULATION TIMER
7.1-1
7.1
PULSE WIDTH MODULATION TIMER
1 OVERVIEW
The S5PC100 has five 32-bit timers. These timers generate internal interrupts to the ARM subsystem. In addition,
Timers 0, 1, and 2 include a Pulse Width Modulation (PWM) function which drives an external I/O signal. The
PWM for timer 0 has an optional dead-zone generator capability to support a large current device. Timer 3 and 4
are internal timers without output pins.
The Timers are normally clocked off of a divided version of the APB-PCLK. Timers 0 and 1 share a programmable
8-bit prescaler that provides the first level of division for the PCLK. Timer 2, 3, and 4 share a different 8-bit
prescaler. Each timer has its own, private clock-divider that provides a second level of clock division (prescaler
divided by 2,4,8, or 16). Alternatively, the Timers can select a clock source from an external pin. Timers 0,1, 2,
3,and 4 selects the external clock (PWM_TCLK )..
Each timer has its own 32-bit down-counter which is driven by the timer clock. The down-counter is initially loaded
from the Timer Count Buffer register (TCNTBn). If the down-counter reaches zero, the timer interrupt request is
generated to inform the CPU that the timer operation is complete. If the timer down-counter reaches zero, the
value of corresponding TCNTBn automatically reloads into the down-counter to start a next cycle. However, if the
timer stops, for example, by clearing the timer enable bit of TCONn during the timer running mode, the value of
TCNTBn is not reloaded into the counter.
The Pulse Width Modulation function (PWM) uses the value of the TCMPBn register. The timer control logic
changes the output level if down-counter value matches the value of the compare register in timer control logic.
Therefore, the compare register determines the turn-on time (or turn-off time) of a PWM output.
The TCNTBn and TCMPBn registers are double buffered to allow the timer parameters to be updated in the
middle of a cycle. The new values do not take effect until the current timer cycle completes.