This feature helps to instantiate the clocking primitive which best fits your requirements, with high performance and better clock routing, while keeping the use of clocking resources to a minimum. All clocking features and optional ports are deselected when you select the primitive as Auto . You need to exclusively enable the options which are required. The following tables explain the selection criteria depending on the clocking features selected.
Note: This feature is available for UltraScale™ and UltraScale+™ devices only.
Feature |
BUFGCE_DIV |
PLL |
MMCM |
Selection Criteria |
Inferred Primitive |
---|---|---|---|---|---|
Phase Alignment |
X |
X |
ü |
|
MMCM |
Spread Spectrum |
X |
X |
ü |
|
MMCM |
Dynamic Phase Shift |
X |
X |
ü |
|
MMCM |
Secondary Input Clock |
X |
X |
ü |
|
MMCM |
Input_clk_stopped |
X |
X |
ü |
|
MMCM |
Clock fb stopped |
X |
X |
ü |
|
MMCM |
More than four output clocks |
X |
X |
ü |
|
MMCM |
Use CDDC |
X |
X |
ü |
|
MMCM |
Dynamic Reconfig |
X |
ü |
ü |
If number of output clocks > 2 |
MMCM |
If number of output clocks ≤ 2 |
PLL |
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Safe Clock Startup |
X |
ü |
ü |
If number of output clocks > 2 |
MMCM |
If number of output clocks ≤ 2 |
PLL |
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Out_freq >In_freq |
X |
ü |
ü |
If number of output clocks > 2 |
MMCM |
If number of output clocks ≤ 2 |
PLL |
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Reset |
X |
ü |
ü |
If number of output clocks > 4 |
MMCM |
If number of output clocks ≤ 4 The clocks must satisfy condition 2 and 3. |
PLL |
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Non zero Phase Shift |
X |
ü |
ü |
If number of output clocks > 2 |
MMCM |
If number of output clocks ≤ 2 |
PLL |
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Locked |
X |
ü |
ü |
If number of output clocks > 4 |
MMCM |
If number of output clocks ≤ 4 The clocks must satisfy condition 2 and 3. |
PLL |
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Power_down |
X |
ü |
ü |
If number of output clocks > 4 |
MMCM |
If number of output clocks ≤ 4 The clocks must satisfy condition 2 and 3. |
PLL |
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Output Buffer selection |
ü |
ü |
ü |
If all output clocks satisfy the conditions 1 and 2 |
BUFGCE_DIV (Supports a maximum of four clocks) |
Else if clocks satisfy condition 2 and 3 |
PLL |
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Else |
MMCM |