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S3C2410A PWM TIMER
10-1
10 PWM TIMER
OVERVIEW
The S3C2410A has five 16-bit timers. Timer 0, 1, 2, and 3 have Pulse Width Modulation (PWM) function. Timer 4 has
an internal timer only with no output pins. The timer 0 has a dead-zone generator, which is used with a large current
device.
The timer 0 and 1 share an 8-bit prescaler, while the timer 2, 3 and 4 share other 8-bit prescaler. Each timer has a
clock divider which 5 different divided signals (1/2, 1/4, 1/8, 1/16, and TCLK). Each timer block receives its own clock
signals from the clock divider, which receives the clock from the corresponding 8-bit prescaler. The 8-bit prescaler is
programmable and divides the PCLK according to the loading value, which is stored in TCFG0 and TCFG1 registers.
The timer count buffer register (TCNTBn) has an initial value which is loaded into the down-counter when the timer is
enabled. The timer compare buffer register (TCMPBn) has an initial value which is loaded into the compare register to
be compared with the down-counter value. This double buffering feature of TCNTBn and TCMPBn makes the timer
generate a stable output when the frequency and duty ratio are changed.
Each timer has its own 16-bit down counter, which is driven by the timer clock. When the down counter reaches
zero, the timer interrupt request is generated to inform the CPU that the timer operation has been completed. When
the timer counter reaches zero, the value of corresponding TCNTBn is automatically loaded into the down counter to
continue the next operation. However, if the timer stops, for example, by clearing the timer enable bit of TCONn
during the timer running mode, the value of TCNTBn will not be reloaded into the counter.
The value of TCMPBn is used for pulse width modulation (PWM). The timer control logic changes the output level
when the down-counter value matches the value of the compare register in the timer control logic. Therefore, the
compare register determines the turn-on time (or turn-off time) of an PWM output.
FEATURE
— Five 16-bit timers
— Two 8-bit prescalers & Two 4-bit divider
— Programmable duty control of output waveform (PWM)
— Auto reload mode or one-shot pulse mode
— Dead-zone generator