UCOS2 timer tick question

Whilst working on getting BACnet MS/TP (RS485 comms) going on the Rabbit system I was tweaking the OS_TICKS_PER_SEC value to try and adjust the task timing.

If I set a value over 99 my serial comms reception stops working reliably. 99 is fine, 100 serial comms bombs out. Does anyone know if there is a significance to setting OS_TICKS_PER_SEC > 99 as there is no mention of this in the documentation and I have so far not been able to track down anythiing in the library source code (the library functions limit it to a range of 8-1024).

BTW I’ve tested this on a BL5S220, an RCM5700 and an RCM6700 with the same result so I don’t think it is just a simple timing issue.

I’m very puzzled at this stage.