mcf5272 Freescale Semiconductor, Inc, mcf5272 Datasheet - Page 410

• Manufacturer Part Number: mcf5272
• Description: Mcf5272 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

PWM Operation
Summary of the main features include:
18.2 PWM Operation
The PWM is a simple free-running counter combined with a pulse width register and a
comparator such that the output is cleared whenever the counter value exceeds the width
register value. When the counter overflows, or “wraps around,” its value becomes less than
or equal to the value of the width register, and the output is set. With a suitable low-pass
filter, the PWM can be used as a digital-to-analog converter.
The width register is double-buffered so that a new value can be loaded for the next cycle
without affecting the current cycle. At the beginning of each period, the value of the width
buffer register is loaded into the width register, which feeds the comparator. This value is
used for comparison during the next cycle. The prescaler contains a variable divider that
can reduce the incoming clock frequency by certain values between 1 and 32768.
18.3 PWM Programming Model
This section describes the registers and control bits in the PWM module. There are three
independent PWM modules, each with its own control and width registers. The memory
map for the PWM is shown in Table 18-1.
0x00C0
0x00C4
0x00C8
0x00D0
0x00D4
0x00D8
18-2
MBAR
Offset
• Double-buffered width register
• Variable-divide prescale
• Three independent PWM modules
• Byte-wide width register provides programmable duty cycle control
PWM Pulse Width Register
PWM Pulse Width Register
PWM Pulse Width Register
PWM Control Register 0
PWM Control Register 1
PWM Control Register 2
0 (PWWD0), [p. 18-4]
1 (PWWD1), [p. 18-4]
2 (PWWD2), [p. 18-4]
(PWCR0), [p. 18-3]
(PWCR1), [p. 18-3]
(PWCR2), [p. 18-3]
[31:24]
Table 18-1. PWM Module Memory Map
MCF5272 User’s Manual
[23:16]
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
[15:8]
[7:0]
MOTOROLA