help with tanner EDA

hi all,
is any one familer with tanner EDA...
if so, may i know if digital circuits like half adder etc can be checked on this tool in the gate level and not transistor leve....
i did draw it using gates but im getting error in t-spce...
the error statesits in subcircuit but its generated by the tool its self..
can any one help me out with this...

thank you