Pulse-Width Modulator (S12PWM8B8CV2)
MC9S12VRP Family Reference Manual Rev. 1.3
282
NXP Semiconductors
9.3.2.7
PWM Clock A/B Select Register (PWMCLKAB)
Each PWM channel has a choice of four clocks to use as the clock source for that channel as described
below.
Read: Anytime
Write: Anytime
5
CON23
Concatenate Channels 2 and 3
0 Channels 2 and 3 are separate 8-bit PWMs.
1 Channels 2 and 3 are concatenated to create one 16-bit PWM channel. Channel 2 becomes the high order
byte and channel 3 becomes the low order byte. Channel 3 output pin is used as the output for this 16-bit
PWM (bit 3 of port PWMP). Channel 3 clock select control-bit determines the clock source, channel 3 polarity
bit determines the polarity, channel 3 enable bit enables the output and channel 3 center aligned enable bit
determines the output mode.
4
CON01
Concatenate Channels 0 and 1
0 Channels 0 and 1 are separate 8-bit PWMs.
1 Channels 0 and 1 are concatenated to create one 16-bit PWM channel. Channel 0 becomes the high order
byte and channel 1 becomes the low order byte. Channel 1 output pin is used as the output for this 16-bit
PWM (bit 1 of port PWMP). Channel 1 clock select control-bit determines the clock source, channel 1 polarity
bit determines the polarity, channel 1 enable bit enables the output and channel 1 center aligned enable bit
determines the output mode.
3
PSWAI
PWM Stops in Wait Mode —
Enabling this bit allows for lower power consumption in wait mode by disabling
the input clock to the prescaler.
0 Allow the clock to the prescaler to continue while in wait mode.
1 Stop the input clock to the prescaler whenever the MCU is in wait mode.
2
PFRZ
PWM Counters Stop in Freeze Mode
— In freeze mode, there is an option to disable the input clock to the
prescaler by setting the PFRZ bit in the PWMCTL register. If this bit is set, whenever the MCU is in freeze mode,
the input clock to the prescaler is disabled. This feature is useful during emulation as it allows the PWM function
to be suspended. In this way, the counters of the PWM can be stopped while in freeze mode so that once normal
program flow is continued, the counters are re-enabled to simulate real-time operations. Since the registers can
still be accessed in this mode, to re-enable the prescaler clock, either disable the PFRZ bit or exit freeze mode.
0 Allow PWM to continue while in freeze mode.
1 Disable PWM input clock to the prescaler whenever the part is in freeze mode. This is useful for emulation.
7
6
5
4
3
2
1
0
R
PCLKAB7
PCLKAB6
PCLKAB5
PCLKAB4
PCLKAB3
PCLKAB2
PCLKAB1
PCLKAB0
W
Reset
0
0
0
0
0
0
0
0
Figure 9-9. PWM Clock Select Register (PWMCLK)
Table 9-10. PWMCTL Field Descriptions (continued)
Note:
Bits related to available channels have functional significance. Writing to unavailable bits has no effect. Read from
unavailable bits return a zero
Field
Description
Summary of Contents for MC9S12VRP64
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