mc9s12e256 Freescale Semiconductor, Inc, mc9s12e256 Datasheet - Page 394

• Manufacturer Part Number: mc9s12e256
• Description: Hcs12 Microcontrollers 16-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 12 Pulse-Width Modulator (PWM8B6CV1)
Read: anytime
Write: anytime (any value written causes PWM counter to be reset to 0x0000).
12.3.2.13 PWM Channel Period Registers (PWMPERx)
There is a dedicated period register for each channel. The value in this register determines the period of
the associated PWM channel.
The period registers for each channel are double buffered so that if they change while the channel is
enabled, the change will NOT take effect until one of the following occurs:
In this way, the output of the PWM will always be either the old waveform or the new waveform, not some
variation in between. If the channel is not enabled, then writes to the period register will go directly to the
latches as well as the buffer.
Reference
394
Reset
Reset
Reset
•
•
•
W
W
W
R
R
R
The effective period ends
The counter is written (counter resets to 0x0000)
The channel is disabled
Section 12.4.2.3, “PWM Period and Duty,”
Bit 7
Bit 7
Bit 7
0
0
0
0
0
0
7
7
7
Reads of this register return the most recent value written. Reads do not
necessarily return the value of the currently active period due to the double
buffering scheme.
Figure 12-18. PWM Channel Counter Registers (PWMCNT3)
Figure 12-19. PWM Channel Counter Registers (PWMCNT4)
Figure 12-20. PWM Channel Counter Registers (PWMCNT5)
6
0
0
6
0
0
6
0
0
6
6
6
MC9S12E256 Data Sheet, Rev. 1.08
5
0
0
5
0
0
5
0
0
5
5
5
NOTE
4
0
0
4
0
0
4
0
0
4
4
4
for more information.
3
3
0
0
3
3
0
0
3
3
0
0
2
0
0
2
0
0
2
0
0
2
2
2
Freescale Semiconductor
1
0
0
1
0
0
1
0
0
1
1
1
Bit 0
Bit 0
Bit 0
0
0
0
0
0
0
0
0
0