block?

[Troward]

just reading NFHS 10.6.1E and wanted to clarify.

A1 is guarded by B1 who is in a legal guarding position with his feet set. A1 beats by B1 by stepping arround him and getting his head & shoulders past the defender. A1's trailing foot catches B1's outside foot which is still planted on the floor. A1 falls to the floor and loses the ball to team B. So A1 was triped but B1 has not moved from his legal position.
Is this a block? charge? no call?

thanks again
GTW