How do you map an abstract UPF power switch to a real library cell with map_power_switch?

Short Answer

map_power_switch (UPF) tells the tools which library cell implements an abstract switch from create_power_switch (UPF). In IEEE 1801-2015 the syntax is the switch name followed by a required -lib_cells list and an optional -port_map. Mapping picks the cell; ICC2 still has to build and connect the physical array.

Technical Explanation

• Syntax: map_power_switch PD_COP_SW -domain PD_COP -lib_cells {HEADER_X4} (UPF). The name matches creation; ICC2 uses -domain as lookup scope and lists no -port_map.
• Library cells: each cell must be defined by define_power_switch_cell (UPF) or carry the switch attributes in Liberty.
• Port association: without -port_map, ports match by name, and any unmatched port on either side is an error.
• -port_map pairs cell ports with switch ports when names differ, including control and acknowledge ports.
• Physical build: create_power_switch_array (ICC2) or create_power_switch_ring (ICC2) place the cells; connect_power_switch (ICC2) chains their controls.
• Map a header cell to a header-style switch: a PMOS header gates VDD, an NMOS footer gates VSS.
• Mapping is explicit, so equivalence checkers may not prove it against the RTL intent.

# [UPF]  mychip.upf
map_power_switch PD_COP_SW -domain PD_COP -lib_cells {HEADER_X4}
# [ICC2]  icc2_shell
report_mv_lib_cells -verbose
check_mv_design

What To Check

• The switch name in the map matches the name in create_power_switch.
• The library cell is a real switch cell and gates the same rail as the UPF switch.
• Every port on the switch and the cell is paired, by name or by -port_map.
• The array built in ICC2 uses the mapped cell.

Healthy, Suspicious & Hard-stop Results

• Healthy (illustrative): report_mv_lib_cells shows HEADER_X4 with its PG pins as a switch cell, and check_mv_design is clean.
• Suspicious (illustrative): The map lists several cells and the array mixes them without a stated reason.
• Hard stop: The map names a switch that does not exist, or a footer cell for a header switch.

What The Interviewer Is Testing

• Do you know mapping selects the cell but does not place it?
• Can you explain named association versus -port_map?

Follow-up Question & Model Response

"What happens if you never map the switch?"

Candidate Model Response: The UPF still describes a legal switch, so simulation and static checks can run. Implementation, though, has no cell to build the array from unless it can pick one from the library itself. You lose control of which switch cell and drive strength end up in silicon. Map it explicitly and check the result with report_mv_lib_cells.