Each clock on the core interface, whether it is a control clock, a reference clock, or a clock to be decoupled, has a parameter FREQ_HZ, which can be used to set the clock frequency. When the core is generated in out-of-context mode, these frequencies are used to set clock constraints on the core instance. The clock frequencies are managed automatically when the IP is used in the IP integrator.
The property names are defined as:
CONFIG.<clock name>.FREQ_HZ
where <clock name> is one of the following:
-
aclk_CLOCK
for the AXI control interface clock. -
decouple_ref_clk_CLOCK
for the decouple signal interface reference clock. -
<interface name>_aclk_CLOCK
for the interface-specific AXI clocks. -
<interface name>_ref_clk_CLOCK
for the interface-specific reference clocks.
Some examples are shown in the following table.
Property Name | Description |
---|---|
CONFIG.aclk_CLOCK.FREQ_HZ | The AXI control interface clock. |
CONFIG.intf_0_CLK_CLOCK.FREQ_HZ | A clock call CLK in an interface of type xilinx.com:signal:clock_rtl:1.0 called intf_0. |
These properties can be set using the standard Vivado
set_property
command. Additional constraints might be required when
decoupling clocks using a BUFGCE primitive or a BUFGCTRL primitive. The Vivado tools treat the data inputs to these primitives as
clock, so the relationship between data input and its control input (the decouple
signal) might need to be defined using constraints.