TRIAC triggering issues?

[George]

I'm trying to trigger a sensitive gate (designed specifically for direct connection to microcontrollers) BT131-600 TRIAC. MT1 is connected to neutral line, so is Vss on the PIC, The triac tho seems to only want to fire on the opposite side of the waveform, ie. when a port = high but with the AC voltage running negative, will not trigger when AC wave form goes positive.but will trigger when going negative like this it doesnt matter where the timing is - or seemingly how long the pulse is - I've tried timing at 90 deg and trigger pulse 100us to 2ms but still behaves the same. Most datasheets for sensitive gate triacs show bi polarity triggering - this datasheet doesnt specify that but perhaps implies. The voltage the circuit is running at is 4V and the resistor to gate is 220R the gate voltage on trigger is about 1 volt so that gives a drive current of about 12mA.

Any clues anyone? Would appreciate any input as I think I've tried most things. Next on the list is to try different model TRIACS

Thx