Stage-7 ADC chain audit. The MMCM SIMULATION model in adc_clk_mmcm.v
takes 4096 DCO cycles (~10 µs at 400 MHz) to assert mmcm_locked. The
existing TB waited only ~5 cycles after each reset deassert, so the
gated reset_n_400m never released and adc_data_valid_400m stayed low
for every test group past the initial reset checks.
Expose mmcm_locked as a new module output on ad9484_interface_400m
(real path) and ad9484_interface_400m_stub (sim path; tied high one
DCO cycle after reset deassert since the stub has no MMCM). Connect
it through to tb_ad9484_xsim.v and add a `wait_for_adc_ready` task
that waits on the lock signal plus 6 DCO cycles for the 2-FF
lock-sync, 2-FF reset-sync, and pipeline drain. Apply the task at
each of the five reset cycles in the testbench.
radar_receiver_final.v: tie the new port off (.mmcm_locked()) — host
status pipeline doesn't surface lock yet, deferred for a future
status-word widening.
Local iverilog regression (36/0/7) clean. xsim verification of the
xsim-only TB itself is pending (remote Vivado host).
Jason
6738f12e54