Modular Input/Output Subsystem (MIOS14)
MPC561/MPC563 Reference Manual, Rev. 1.2
17-38
Freescale Semiconductor
where:
•
N
MCPSM
is the overall MCPSM clock divide ratio (2, 3, 4,...,16).
•
N
COUNTER
is the divide ratio of the prescaler of the counter (used as a time reference) that drives
the 16-bit counter bus.
•
N
MDASM
is the maximum count reachable by the counter when using n bits of resolution (this
count is equal to 2
n
).
A few examples of frequencies and resolutions that can be obtained are shown in
When using 16 bits of resolution on the comparator (MODE[2:0] = 0b000), the output can vary from a 0%
duty cycle up to a duty cycle of 65535/65536. In this case it is not possible to have a 100% duty cycle. In
cases where 16-bit resolution is not needed, it is possible to have a duty cycle ranging from 0% to 100%.
Setting bit 15 of the value stored in register B to one results in the output being ‘always set’. Clearing bit
15 (to zero) allows normal comparisons to occur and the normal output waveform is obtained. Changes to
and from the 100% duty cycle are done synchronously on an A or B match, as are all other width changes.
Table 17-17. MDASM PWM Example Output Frequencies/Resolutions at f
SYS
= 40 MHz
Resolution
(bits)
N
MCPSM
N
COUNTER
N
MDASM
PWM output frequency (Hz)
1
1
This information is valid only if the MDASM is connected to an MMCSM operating as a free-running
counter.
16
16
256
65536
0.15
16
2
1
65536
305.17
15
16
256
32768
0.29
15
2
1
32768
610.35
14
16
256
16384
0.59
14
2
1
16384
1 220.70
13
16
256
8192
1.19
13
2
1
8192
2 441.41
12
16
256
4096
2.38
12
2
1
4096
4 882.81
11
16
256
2048
4.77
11
2
1
2048
9 765.63
9
16
256
512
19.07
9
2
1
512
39 062.50
7
16
256
128
76.29
7
2
1
128
156 250
f
PWM
=
f
SYS
N
MCPSM
• N
COUNTER
• N
MDASM
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...