ARINC429 in channel RX5
Radar Altimeter uses ARINC 429 Label 164
The PFD expects the label to conform to the ARINC 429 specification with an equipment ID of 007, which means:
16 significant bits (bits 28-13), with a scale of 0.125 feet per bit and a maximum value of 8192 feet (per the data format)
The PFD will mark radar altitudes greater than 2500 feet as invalid.
The PFD will accept that label with SDI bits of 0 or 1. SDI bits are bits 9 & 10 of the 429 word.