Every wire from the switchable domain into the always-on domain is a wire that will one day float, and the always-on logic downstream will read that float as something. Isolation is the set of clamps that decide what that something is, and retention is the companion decision about what comes back afterwards. NanoSoC needs exactly 114 clamps in four groups, asserted in a strict order around reset and the switch, and this topic counts them, times them and shows the intent that generates them. For the cell-level mechanism see Isolation Strategies; this topic teaches the integration view the course owns.
Lesson | After it you can... |
|---|---|
List every PD_SW to PD_AON signal group and prove the 114 total. | |
Order isolate, reset and switch, and review a sequence for the one inversion that breaks it. | |
Read the UPF intent for NanoSoC and name what the integrator checks versus what the tools generate. |
Suggested order: top to bottom. Count the clamps first, because the timing lesson enables exactly that set; then learn the order, because UPF intent is just this order written in a standard form. Readers debugging a sleep-wake loop should start at the second lesson.
Because only powered-off outputs float. Signals from PD_AON into PD_SW drive into dead logic, which wastes nothing and corrupts nothing that survives; the 114 count covers the floating direction only.