Structure of weakly invertible semi-input-memory finite automata with delay 2

Semi-input-memory finite automata, a kind of finite automata introduced by the author of this paper for studying error propagation, are a generalization of input-memory finite automata by appending an autonomous finite automaton component. This paper gives a characterization on the structure of weakly invertible semi-input-memory finite automata with delay 2 in which input alphabets and output alphabets have two elements and autonomous finite automata are cyclic. For the structure of feedforward inverse finite automata with delay 2, Zhu first gave a characterization; from a result on mutual invertibility of finite automata, the result mentioned above also leads to a different characterization on the structure of feedforward inverse finite automata with delay 2.