User's Manual

PMAC2A PC104 Hardware Reference Manual
Hardware Setup 7
Connect pin 1 to 2 to tie differential line to +2.5V
Tie to +2.5V when no connection
Tie to +2.5V for single-ended encoders
Connect pin 2 to 3 to tie differential line to +5V
Don’t care for differential line driver encoders
Tie to +5V for complementary open-collector encoders (obsolete)