mc68hc11k4 Freescale Semiconductor, Inc, mc68hc11k4 Datasheet - Page 213

• Manufacturer Part Number: mc68hc11k4
• Description: Mc68hc11k1 Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

9.9.2 Pulse-Width Modulation Control Registers
9.9.2.1 Pulse-Width Modulation Timer Clock Select Register
M68HC11K Family
MOTOROLA
Address: $0060
Figure 9-31. Pulse-Width Modulation Timer Clock Select (PWCLK)
The three clocks are derived from the E clock by writing to registers
which determine their scaling factors. The clock A frequency is equal to
E divided by 1, 2, 4, or 8, depending on which bits (PCKA[2:1]) in the
PWCLK register are set. The clock B frequency is equal to the E clock
divided by a power of two determined by bits PCKB[3:1] in the PWCLK
register. Clock S is derived by dividing clock A by the integer (1 to 256)
stored in the PWSCAL register, then by two.
Two channels can be concatenated by setting the appropriate bit
(CON34 or CON12) in the PWCLK register. In this mode, the clock
source is determined by the low-order channel, which is channel two in
CON12 and channel four in CON34. The output is also placed on the pin
associated with the low-order channels, so when two channels are
concatenated the pin associated with the high-order channel (PH0
and/or PH2) can be used for GPIO. A read of the high-order byte causes
the low-order byte to be latched for one cycle to guarantee that
double-byte reads are accurate. A write to the low-order byte of the
counter causes reset of the entire counter. A write to the high-order byte
of the counter has no effect.
The PWM control registers are described here.
Reset:
Read:
Write:
Freescale Semiconductor, Inc.
For More Information On This Product,
CON34
Bit 7
0
Go to: www.freescale.com
CON12
Timing System
6
0
PCKA2
5
0
PCKA1
4
0
3
0
0
Pulse-Width Modulator (PWM)
PCKB3
2
0
PCKB2
1
0
Timing System
Technical Data
PCKB1
Bit 0
0
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