Samsung S3C2451X User Manual page 313

S3C2451X RISC MICROPROCESSOR
13
OVERVIEW
The S3C2451X 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 generates 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 internal down-counter when
the timer is enabled. The timer compare buffer register (TCMPBn) has an initial value, which is loaded into the
internal compare register to be compared with the internal 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 internal down counter, which is driven by the timer clock. When the internal down-
counter reaches zero, the timer interrupt request is generated to inform the CPU that the timer operation has been
completed. When the timer internal down-counter reaches zero, the value of corresponding TCNTBn is
automatically loaded into the internal 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 internal down-counter.
The value of TCMPBn is used for pulse width modulation (PWM). The timer control logic changes the output level
when the internal down-counter value matches the value of the internal compare register in the timer control logic.
Therefore, the internal compare register determines the turn-on time (or turn-off time) of a 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
PWM TIMER
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
PWM TIMER
13-1