An encoder includes an encoding unit configured to receive 2n-bit read data and to generate 2m-bit read data, and an output driver configured to input m-bit first read data of the 2m-bit read data, to transmit voltage and/or current a first number of times corresponding to a number of first bits indicating a first state included in the m-bit first read data or to transmit current corresponding to the number of first bits during an activation period of a clock signal, and to transmit the voltage and/or the current a second number of times corresponding to a number of second bits indicating the first state included in m-bit second read data of the 2m-bit read data or to transmit current corresponding to the number of second bits during a deactivation period of the clock signal, wherein n is at least 2 and m is at least 3.