To count the number of symbols based on a byte clock by making a counted value to coincide with the number of symbols by increasing or decreasing the counted value of a main counter by every specified data byte.

A start signal is received from a state machine controller 3 similarly as an accumulator 2 and the signal is counted down by every byte clock by a Y value counter 6 as an adjustment counter. When a specified relation between the byte clock and a symbol clock is established, a value of the Y value counter 6 is reset and a value of the accumulator 2 is simultaneously decreased by a specified adjusted value by a multiplexer 5 as a subtracter to subtract and decrement the value of the accumulator 2 one by one by every byte clock in normal operation. Namely, the counted value is made to coincide with the number of symbols by increasing or decreasing the counted value of the main counter by using the adjusted value to be determined based on ratio between the number of bits to constitute one byte and the number of bits to constitute one symbol.