I suspect (educated guess...) that the FADEC senses IEPR on a Roller.
On an RB211, it does sense integrated EPR. The 777 Trent seems to be simplified, however. It only measures fan inlet pressure (P2.0) and the low pressure/hot turbine exhaust pressure (P5.0).
This seems unusual to me as most of the thrust comes from the fan exhaust, not the core.
P2.0 probes are heated. Failure of heating would be evident on the flight deck (but failures like this simply don't happen at the same time... and even if both heaters failed, the crew would still be able to power up the engines)
Probe heat is monitored by both channels of the EEC. On the 777, probe heat is activated at
5%
N1 (rather than
50%
N3 on the RB211)
Rgds.
NSEU