mc68hc908lb8 Freescale Semiconductor, Inc, mc68hc908lb8 Datasheet - Page 158

• Manufacturer Part Number: mc68hc908lb8
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Pulse Width Modulator with Fault Input (PWM)
PRSC1 and PRSC0 — PWM Prescaler Bits
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.
MAP1 — Disable Map for PWM1 Bit
MAP0 — Disable Map for PWM0 Bit
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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.
These buffered read/write bits allow the PWM clock frequency to be modified as shown in
This write-once bit allows the user to select PWM1 to be disabled when a logic 1 is present on the
FAULT pin.
This write-once bit allows the user to select PWM0 to be disabled when a logic 1 is present on the
FAULT pin.
1 = PWM0 has positive polarity
0 = PWM0 has negative polarity
1 = Disables PWM1 when an external fault occurs
0 = Prevents PWM1 from being disabled by hardware
1 = Disables PWM0 when an external fault occurs
0 = Prevents PWM0 from being disabled by hardware
Address:
When reading these bits, the value read is the buffer value (not necessarily
the value the PWM generator is currently using).
Reset:
Figure 15-22. PWM Disable Mapping Write-Once Register (DISMAP)
Read:
Write:
$004D
Bit 7
0
0
= Unimplemented
PRSC1 and PRSC0
6
0
0
Prescaler Bits
MC68HC908LB8 Data Sheet, Rev. 1
Table 15-5. PWM Prescaler
00
01
10
11
5
0
0
NOTE
4
0
0
3
0
0
PWM Clock
Frequency
BUSCLK/2
BUSCLK/4
BUSCLK/8
BUSCLK
2
0
0
MAP1
1
1
Freescale Semiconductor
MAP0
Bit 0
1
Table
15-5.