Differential encoding device in cable modem

摘要

The present invention relates to a differential encoding apparatus in a cable modem, and is comprised of a difference bit calculator and a 2-bit digital storage element.;In this case, the difference bit calculator performs a differential encoding of the digital signal, and the 2-bit digital storage element performs a function of delaying the output signal of the difference bit calculator by one period and then returning it to the input terminal of the difference bit calculator .;The difference bit calculator comprises a first multiplexer for outputting the upper bits of the differential coded signal for the digital signal and a second multiplexer for outputting the lower bits in the first embodiment.;On the other hand, in the second embodiment, the two-bit signals to be subjected to differential encoding are denoted by C1 and C0, the signals output one cycle before by the differential bit calculator are denoted by P1 and P0, and the exclusive OR gate element is defined by XOR , XOR1 receiving P1 and P0, XOR2 receiving C1 and C0 as input signals, XOR3 receiving P1 and C1 as input signals, and inverter device receiving XOR4 and XOR1 output signals receiving input signals as P0 and C0 as input signals An AND gate element for receiving the output signal of XOR2 and the output signal of the inverter element as an input signal, the output signal of the AND gate element and XOR5 receiving the output signal of XOR3 as an input signal, and the output signal of the AND gate element and the output signal of XOR4 As an input signal.