Visible to Intel only — GUID: mwh1452708858001
Ixiasoft
Externally Switched Clock
Through an external multiplexer or jumper setting, digital systems are capable of providing different clock frequencies to the same clock port. The Timing Analyzer can model this behavior with the create_clock constraint and the -add option. The following figure shows a simple register-to-register path where you can drive the clock port clock with a 100-MHz clock or a 50-MHz clock.
Figure 8. Simple Register-to-Register Design
Externally Switched Clock Constraints
# The clk port can be driven at 100MHz (10ns) or
# 50MHz (20ns)
# clkA is 10ns
create_clock \
-period 10.000 \
-name clkA \
[get_ports {clk}]
# clkB is 20ns assigned to the same port
# Requires -add option
create_clock \
-period 20.000 \
-name clkB \
[get_ports {clk}] \
-add
set_clock_groups \
-exclusive \
-group {clkA} \
-group {clkB}