SC9S12XS256J1MAA FREESCALE [Freescale Semiconductor, Inc], SC9S12XS256J1MAA Datasheet - Page 384

• Manufacturer Part Number: SC9S12XS256J1MAA
• Description: HCS12 Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Pulse-Width Modulator (S12PWM8B8CV1)
13.4.2
The main part of the PWM module are the actual timers. Each of the timer channels has a counter, a period
register and a duty register (each are 8-bit). The waveform output period is controlled by a match between
the period register and the value in the counter. The duty is controlled by a match between the duty register
and the counter value and causes the state of the output to change during the period. The starting polarity
of the output is also selectable on a per channel basis. Shown below in
for the PWM timer.
13.4.2.1
Each PWM channel has an enable bit (PWMEx) to start its waveform output. When any of the PWMEx
bits are set (PWMEx = 1), the associated PWM output signal is enabled immediately. However, the actual
PWM waveform is not available on the associated PWM output until its clock source begins its next cycle
due to the synchronization of PWMEx and the clock source. An exception to this is when channels are
concatenated. Refer to
384
Clock Source
PWMEx
(Clock Edge
PWM Channel Timers
PWM Enable
Sync)
Gate
The first PWM cycle after enabling the channel can be irregular.
Up/Down
Section 13.4.2.7, “PWM 16-Bit Functions”
8-Bit Counter
Figure 13-19. PWM Timer Channel Block Diagram
PWMCNTx
Q
Q
Reset
S12XS Family Reference Manual, Rev. 1.09
T
R
NOTE
8-bit Compare =
8-bit Compare =
PWMPERx
PWMDTYx
CAEx
for more detail.
Figure 13-19
T
R
Q
Q
PPOLx
From Port PWMP
M
U
Data Register
X
Freescale Semiconductor
is the block diagram
M
U
X
To Pin
Driver