Assume a division by 2.125 is required, then:
• Counter A would take phase 0 (0 degrees) of the VCO
• Counter B would take as start phase 2 (45 degree offset)
Output starts High with rising edge on counter A and goes Low with second rising edge counter B. It goes High again with next rising edge of counter B, counter B switches to VCO phase 90 and the output goes Low again by the second rising edge of that phase and so on.
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X-Ref Target - Figure 3-25 
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Reg 04 |
ADDR: 0x04 |
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
|
Default |
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1 |
0 |
0 |
1 |
1 |
1 |
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Access |
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R/W |
R/W |
R/W |
R/W |
R/W |
R/W |
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5:3 |
mc_ss_steps_init[2:0] |
Start the correct spread based on the SS_MODE attribute. Default value is 100 . |
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2:0 |
mc_ss_steps[2:0] |
Control the spread of the spread-spectrum clocking based on the SS_MODE attribute. Default value is 111 . |
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The settings for register 4 are controlled by the SS_MODE attribute of the MMCM. Refer to the Spread-Spectrum Clock Generation section for detailed information on spread-spectrum clocking set up and behavior.
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|
ss_steps_init |
ss_steps |
|---|---|---|
|
DOWN_LOW |
100 |
011 |
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DOWN_HIGH |
100 |
011 |
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CENTER_LOW |
100 |
111 |
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CENTER_HIGH |
100 |
111 |
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Reg 00 |
ADDR: 0x00 |
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Bit |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
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Default |
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0 |
0 |
0 |
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Access |
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R/W |
R/W |
R/W |
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3 |
mc_inv_clkfbin |
Enable inversion on the CLKFBIN input. This is the same as setting the attribute IS_CLKFBIN_INVERTED to 1. |
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2 |
mc_inv_clkin2 |
Enable inversion on the CLKIN2 input. This is the same as setting the attribute IS_CLKIN2_INVERTED to 1. |
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|
1 |
mc_inv_clkin1 |
Enable inversion on the CLKIN1 input. This is the same as setting the attribute IS_CLKIN1_INVERTED to 1. |
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Register 0 represents the bits that are also available as attributes of the MMCM primitive. For the functional explanation of these bits, refer to the MMCM Attributes section.