This feature helps instantiating the clocking primitive that best fits your requirements with minimum usage of clocking resources, high performance, and better clock routing. All clocking features and optional ports would be in unselected state when you select primitive as Auto. You need to exclusively enable the options that are required. The following table explains the selection criteria depending on the clocking features that you select.
Feature | Auto Primitive Selection | Selection Criteria |
---|---|---|
Phase Alignment | MMCM | This feature is only supported in MMCM |
Dynamic Phase Shift | MMCM or DPLL or MBUFGCE | The selection criteria is:
|
Secondary Input Clock | MMCM | This feature is only supported in MMCM |
Number Output Clocks selected > 4 | MMCM or DPLL or MBUFGCE | The selection criteria is:
|
Safe Clock Startup and Safe Clock Mode as Deskew Mode | MMCM | DESKEW Mode is not supported for DPLL, as
clkin_deskew connection must not come from
clk_out path |
Non zero Phase | MMCM or DPLL | The selection criteria is:
|
Input Clock Stopped (port) | MMCM | This port is available only in MMCM |
Clkfb_stopped (port) | MMCM | This port is available only in MMCM |
Reset, Locked, Power_down Port Input Frequency Ranges, Output Frequency ranges, and VCO Frequency RangesNote: The range values will vary depending on
the part/board/speed grade selected. Refer to
Versal
AI Core Series Data Sheet: DC and AC Switching
Characteristics (DS957) for DC and AC switching
characteristics.
|
MMCM OR DPLL | MMCM as AUTO_PRIMITIVE is chosen when:
Note: Reset and power down are mapped to the same port.
For backward compatibility, reset is shown as a port.
|
Output Clocks <= 4 | DPLL | If Duty Cycle of all clocks = 50% |
MMCM | If any clock Duty Cycle != 50% | |
MBUFGCE | If Duty Cycle of all clocks = 50% and phase of all
clocks = 0 and clock grouping of all clocks is Auto and all the output
clock frequencies are integer divides to each other (/1, /2, /4 and
/8) For example: Four clock outs are present with above criteria and having frequencies as ck_out1 = 200 MHz, clk_out2 = 100 MHz, clk_out3 = 50 MHz and ck_out4 = 25 MHz. In this case MBUFGCE is inferred as Auto Primitive as the clocks are divides to each other |
|
ZHOLD | DPLL | The selection criteria is: If the number of output clocks ≤ 4 with ZHOLD is enabled and the selected output clocks ≤ 500 MHz at 50% Duty Cycle, then the DPLL is set to Auto Primitive |