mm912f634 Freescale Semiconductor, Inc, mm912f634 Datasheet - Page 95

• Manufacturer Part Number: mm912f634
• Description: Mm912f634 - Integrated S12 Based Relay Driver With Lin
• Manufacturer: Freescale Semiconductor, Inc

Note:
Functional Description and Application Information
4.13.3.7
There is a dedicated duty register for each channel. The value in this register determines the duty of the associated PWM
channel. The duty value is compared to the counter and if it is equal to the counter value a match occurs and the output changes
state.
The duty registers for each channel are double buffered, so 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 duty waveform or the new duty waveform, not some variation in
between. If the channel is not enabled, then writes to the duty register will go directly to the latches as well as the buffer.
See
To calculate the output duty cycle (high time as a% of period) for a particular channel:
For boundary case programming values, please refer to
Freescale Semiconductor
Offset
86.
Reset
W
R
•
•
•
•
•
Section 4.13.4.2.3, “PWM Period and Duty"”
(86)
Offset related to 0x0200 for blocking access and 0x300 for non blocking access within the global address space.
The effective period ends
The counter is written (counter resets to $00)
The channel is disabled
Polarity = 0 (PPOL x =0)
Polarity = 1 (PPOLx = 1)
0x68/0x69
– Duty Cycle = [(PWMPERx-PWMDTYx)/PWMPERx] * 100%
– Duty Cycle = [PWMDTYx / PWMPERx] * 100%
Bit 7
PWM Channel Duty Registers (PWMDTYx)
7
0
Reads of this register return the most recent value written. Reads do not necessarily return
the value of the currently active duty due to the double buffering scheme.
Depending on the polarity bit, the duty registers will contain the count of either the high time
or the low time. If the polarity bit is one, the output starts high and then goes low when the
duty count is reached, so the duty registers contain a count of the high time. If the polarity
bit is zero, the output starts low and then goes high when the duty count is reached, so the
duty registers contain a count of the low time.
6
0
6
Figure 24. PWM Channel Duty Registers (PWMDTYx)
0
5
5
for more information.
Section 4.13.4.2.7, “PWM Boundary
NOTE
NOTE
0
4
4
0
3
3
0
2
2
PWM Control Module (PWM8B2C)
Cases"”.
1
0
1
Access: User read/write
MM912F634
Bit 0
0
0
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