Clock Conditioning Circuits in IGLOO and ProASIC3 Devices
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constraint file. Layout will fail if the global assignments are not allocated properly. See the
the quadrant clock networks.
Promoted global signals will be instantiated with CLKINT macros to drive these signals onto the
global network. This is automatically done by Designer when the Auto-Promotion option is
selected. If the user wishes to assign the signals to the quadrant globals instead of the default chip
globals, this can done by using ChipPlanner, by declaring a physical design constraint (PDC), or by
importing a PDC file.
Physical Constraints for Quadrant Clocks
If it is necessary to promote global clocks (CLKBUF, CLKINT, PLL, CLKDLY) to quadrant clocks, the
user can define PDCs to execute the promotion. PDCs can be created using PDC commands (pre-
compile) or the MVN interface (post-compile). The advantage of using the PDC flow over the MVN
flow is that the Compile stage is able to automatically promote any regular net to a global net
before assigning it to a quadrant. There are three options to place a quadrant clock using PDC
commands:
Place a clock core (not hardwired to an I/O) into a quadrant clock location.
Place a clock core (hardwired to an I/O) into an I/O location (set_io) or an I/O module
location (set_location) that drives a quadrant clock location.
Assign a net driven by a regular net or a clock net to a quadrant clock using the following
command:
assign_local_clock -net <net name> -type quadrant <quadrant clock region>
where
<net name>
is the name of the net assigned to the local user clock region.
<quadrant clock region>
defines which quadrant the net should be assigned to. Quadrant
clock regions are defined as UL (upper left), UR (upper right), LL (lower left), and LR (lower
right).
Note: If the net is a regular net, the software inserts a CLKINT buffer on the net.
For example:
assign_local_clock -net localReset -type quadrant UR
Keep in mind the following when placing quadrant clocks using MultiView Navigator:
Hardwired I/O–Driven CCCs
Find the associated clock input port under the Ports tab, and place the input port at one of
the Gmn* locations using PinEditor or I/O Attribute Editor, as shown in
Figure 4-28.
Figure 4-28 Port Assignment for a CCC with Hardwired I/O Clock Input