Datasheet

PWM Register Descriptions
M68HC12B Family Data Sheet, Rev. 9.1
Freescale Semiconductor 131
11.2.4 PWM Prescale Counter
Read: Anytime
Write: Only in special mode (SMOD = 1)
PWPRES is a free-running 7-bit counter.
11.2.5 PWM Scale Register 0
Read: Anytime
Write: Anytime
A write causes the scaler counter PWSCNT0 to load the PWSCAL0 value unless it is in special mode with
DISCAL = 1 in the PWTST register.
PWM channels 0 and 1 can select clock S0 (scaled) as its input clock by setting the control bit PCLK0
and PCLK1 respectively. Clock S0 is generated by dividing clock A by the value in the PWSCAL0 register
plus one and dividing again by two. When PWSCAL0 = $FF, clock A is divided by 256 then divided by two
to generate clock S0.
11.2.6 PWM Scale Counter 0 Value
Read: Anytime
PWSCNT0 is a down-counter that, upon reaching $00, loads the value of PWSCAL0.
Address: $0043
Bit 7654321Bit 0
Read: 0
Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Write:
Reset:00000000
= Unimplemented
Figure 11-7. PWM Prescale Counter (PWPRES)
Address: $0044
Bit 7654321Bit 0
Read:
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Write:
Reset:00000000
Figure 11-8. PWM Scale Register 0 (PWSCAL0)
Address: $0045
Bit 7654321Bit 0
Read: Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Write:
Reset:00000000
= Unimplemented
Figure 11-9. PWM Scale Counter Register 0 (PWSCNT0)