vsc055xkm-01 Maxim Integrated Products, Inc., vsc055xkm-01 Datasheet - Page 87

• Manufacturer Part Number: vsc055xkm-01
• Description: Enhanced I?c Backplane Controller
• Manufacturer: Maxim Integrated Products, Inc.

VSC055-01
Data Sheet
3.2.79 98h-9Fh: Pulse-Width Modulation Control (PWMC0-PWMC7)
Table 7. Pulse-Width Percentages
These eight registers provide a pulse-width modulated output that can optionally be made available on
each of the Port 1 I/O pins. Configurations for these I/O pins that may have been previously enabled
through other control registers are overridden if either one or both of the PWBF bits are set. The PWBF
bits have higher priority control over the Port 1 I/O pins than any other mode of operation. The pulse-width
modulated outputs are based on a 32-step counter and provide values from a 3.125% to a 100% duty cycle
in 3.125% increments
The following table shows the bit assignments for the Pulse-Width Modulation Control registers.
The following table shows the available percentages of high time for the pulse width for the PWP4-0 bits.
Register Name:
Address:
Reset Value:
Bit
6:5
4:0
PWP4
0
0
0
0
0
0
0
0
0
0
0
0
0
Bit Label
PWBF1-0
PWP4-0
PWP3
0
0
0
0
0
0
0
0
1
1
1
1
1
PWMC0-PWMC7
98h-9Fh
X000_0000b
.
PWP2
0
0
0
0
1
1
1
1
0
0
0
0
1
Access
R/W
R/W
PWP1
0
0
1
1
0
0
1
1
0
0
1
1
0
Description
Pulse-Width Base Frequency
These two bits determine the base operating frequency of the pulse-width
modulated output. These frequencies vary with the input clock rate and are
nominally based on a 10.0 MHz clock source. The available base frequencies
are as follows.
Pulse-Width Percentage
These five bits determine the percentage of high time that the output pulse
contains. There are 32 steps that can be adjusted in 3.125% increments. For
the available percentages of high time, see
PWBF1
87 of 133
0
0
1
1
PWP0
0
1
0
1
0
1
0
1
0
1
0
1
0
PWBF0
Pulse-Width Percentage
3.125% on/high time
6.25% on/high time
9.375% on/high time
12.5% on/high time
15.625% on/high time
18.75% on/high time
21.875% on/high time
25.0% on/high time
28.125% on/high time
31.25% on/high time
34.375% on/high time
37.5% on/high time
40.625% on/high time
0
1
0
1
Pulse-Width Base Frequency
Normal operation—control is provided through
GPD1/DDP1 or BCP1
26 kHz base frequency
52 kHz base frequency
104 kHz base frequency
Table 7,
page 87.
January 2008
Revision 4.1