AR# 1066: XBLOX 5.x: ONE_HOT COUNTER with unconnected UP/DN pin results in DOWN counter
XBLOX 5.x: ONE_HOT COUNTER with unconnected UP/DN pin results in DOWN counter
Keywords: XBLOX, one hot counter, up/down, counter
The XBLOX Reference/User Guide specifies that an XBLOX counter with the UP/DN pin unconnected will default to an up counter. However, if STYLE=ONE_HOT, a DOWN counter will be created. (The "hot" bit, for example, will step from bit 1 to bit 0, instead of from bit 1 to bit 2 as expected.)
To synthesize a ONE_HOT up counter, attach the COUNTER's UP/DN pin to VCC.