I've googled a lot so I've checked the usual things (see below)

Problems: No RPM showing in Mach3,

Data: [YES] Mach3 IS showing consistent indexpulses
[YES] I am starting spindle with Mach 3 "spindle button" or M3 in MDI

ALSO when using this board andMach3 *TURN* code will run to G76 lineand then "waiting for trigger"

Checks:[YES]Selected Pulley is set to Ratio=1 , mach3 throws appropriate error ifspeed is out of range of selected pulley ( setting S number in DRO…as a test asmy spindle is simple on off by M3/ relay)
Index pulse sensor is mounted onspindle
Pulses are clean on scope andlong enough in duration , very consistent
I am using a JNC-40M USB controller board and Index pulses are consistently triggered in Mach3
[YES] Debounce interval and timeare both 0,0 higher numbers make no difference (probably not relevant in my case anyway,since using USB Controller board)
Spindle feedback and averaging are both checked/on

Could the code thatOEM DRO 39 calls be incorrect? Can a user examine/edit it somehow?
(note: probably NOTthe problem as Mach3 is also notrecognizing index pulse as a valid threading trigger)

mill Xml attached