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Semiconductor Group
90
On-Chip Peripheral Components
Figure 7-37
Function of Compare Mode 0
Modulation Range in Compare Mode 0
Generally it can be said that for every PWM generation in compare mode 0 with n-bit wide compare
registers there are 2
n
different settings for the duty cycle. Starting with a constant low level (0% duty
cycle) as the first setting, the maximum possible duty cycle then would be
This means that a variation of the duty cycle from 0% to real 100% can never be reached if the
compare register and timer register have the same length. There is always a spike which is as long
as the timer clock period.
This "spike" may either appear when the compare register is set to the reload value (limiting the
lower end of the modulation range) or it may occur at the end of a timer period. In a timer 2/CCx
register configuration in compare mode 0 this spike is divided into two halves: one at the beginning
when the contents of the compare register is equal to the reload value of the timer; the other half
when the compare register is equal to the maximum value of the timer register (here: 0FFFFH).
Please refer to figure 7-38 where the maximum and minimum duty cycle of a compare output signal
is illustrated. Timer 2 is incremented with the machine clock (
f
OSC
/12), thus at 12-MHz operational
frequency, these spikes are both approx. 500 ns long.
MCT01906
Timer Count = FFFF
Timer Count =
Compare Value
Contents
of
Timer 2
Timer Count = Reload Value
Interrupt can be generated
on overflow
Compare
Output
(P1.x/CCx)
Interrupt can be generated
on compare-match
~ ~
~ ~
H
(1 – 1/2
n
) x 100%
*
Summary of Contents for SAB 80515 Series
Page 9: ...Semiconductor Group 9 Introduction Figure 1 2 Block Diagram ...
Page 12: ...Semiconductor Group 12 Fundamental Structure Figure 2 1 Detailed Block Diagram ...
Page 18: ...Semiconductor Group 18 Central Processing Unit Figure 3 1 Fetch Execute Sequence ...
Page 73: ...Semiconductor Group 73 On Chip Peripheral Components Figure 7 25 A D Converter Block Diagram ...
Page 83: ...Semiconductor Group 83 On Chip Peripheral Components Figure 7 33 a Timer 2 Block Diagram ...
Page 215: ...Device Specifications Semiconductor Group 215 ...
Page 217: ...Device Specifications Semiconductor Group 217 Pin Configuration P LCC 68 ...
Page 219: ...Device Specifications Semiconductor Group 219 Logic Symbol ...
Page 226: ...Device Specifications Semiconductor Group 226 Figure 1 Block Diagram ...
Page 229: ...Device Specifications Semiconductor Group 229 Figure 2 Memory Address Spaces ...
Page 239: ...Device Specifications Semiconductor Group 239 Figure 4 Block Diagram of the A D Converter ...
Page 241: ...Device Specifications Semiconductor Group 241 Figure 5 Interrupt Request Sources ...
Page 242: ...Device Specifications Semiconductor Group 242 Figure 6 Interrupt Priority Level Structure ...