C515A_9708 Datasheet, PDF (85/182 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

On-Chip Peripheral Components
C515A
a) CCHx/CCLx = 0000 or _H = CRCH/CRCL (maximum duty cycle)
P1.x
H
L
Appr. 1/2 Machine Cycle
b) CCHx/CCLx = FFFF _H (minimum duty cycle)
Appr. 1/2 Machine Cycle
P1.x
H
L
MCT01907
Figure 6-18
Modulation Range of a PWM Signal, generated with a Timer 2/CCx Register Combination in
Compare Mode 0*
The following example shows how to calculate the modulation range for a PWM signal. To calculate
with reasonable numbers, a reduction of the resolution to 8-bit is used. Otherwise (for the maximum
resolution of 16-bit) the modulation range would be so severely limited that it would be negligible.
Example:
Timer 2 in auto-reload mode; contents of reload register CRC = FF00H
Restriction of modulation range = 1 / 256 x 2 x 100% = 0.195%
This leads to a variation of the duty cycle from 0.195% to 99.805% for a timer 2/CCx register
configuration when 8 of 16 bits are used.
Semiconductor Group
6-34
1997-08-01