MC68HC908LB8_05 Datasheet, PDF (158/234 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Pulse Width Modulator with Fault Input (PWM)
POL0 — This read/write bit selects the polarity of the PWM waveform of PWM1. Positive polarity
means that when the PWM is active the PWM output is high. Conversely, negative polarity means that
when the PWM is active the PWM output is low.
1 = PWM0 has positive polarity
0 = PWM0 has negative polarity
PRSC1 and PRSC0 — PWM Prescaler Bits
These buffered read/write bits allow the PWM clock frequency to be modified as shown in Table 15-5.
NOTE
When reading these bits, the value read is the buffer value (not necessarily
the value the PWM generator is currently using).
Table 15-5. PWM Prescaler
Prescaler Bits
PRSC1 and PRSC0
00
01
10
11
PWM Clock
Frequency
BUSCLK
BUSCLK/2
BUSCLK/4
BUSCLK/8
15.8.6 PWM Disable Mapping Write-Once Register
The PWM disable mapping write-once register (DISMAP) contains two bits that control the PWM pins that
will be disabled if an external fault occurs. After this register is written for the first time, it cannot be
rewritten unless a reset occurs.
Address: $004D
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
0
0
0
0
0
MAP1
MAP0
Write:
Reset:
0
0
0
0
0
0
1
1
= Unimplemented
Figure 15-22. PWM Disable Mapping Write-Once Register (DISMAP)
MAP1 — Disable Map for PWM1 Bit
This write-once bit allows the user to select PWM1 to be disabled when a logic 1 is present on the
FAULT pin.
1 = Disables PWM1 when an external fault occurs
0 = Prevents PWM1 from being disabled by hardware
MAP0 — Disable Map for PWM0 Bit
This write-once bit allows the user to select PWM0 to be disabled when a logic 1 is present on the
FAULT pin.
1 = Disables PWM0 when an external fault occurs
0 = Prevents PWM0 from being disabled by hardware
MC68HC908LB8 Data Sheet, Rev. 1
158
Freescale Semiconductor