Communication device
A communication device includes a current information storage unit 130 that stores the bit boundary signal at each of timings at which a sampling clock is updated, a past information storage unit 140 that takes in and stores a signal stored in the current information storage unit 130 when a variation point of a reception signal is detected, and does not update a signal stored therein when no variation point of the reception signal is detected, and a clock selection unit 44 that selects CLKSEL 2 used for the sampling of the reception signal from N-phase clocks based on a signal stored in the current information storage unit 130 when a variation point of the reception signal is detected, and selects CLKSEL 3 based on a signal stored in the past information storage unit 140 when no variation point of the reception signal is detected.
1. A communication device that receives a reception signal including a synchronous word and a payload in each frame and samples the reception signal by using one sampling clock selected from N-phase clocks (N is an integer equal to or greater than two), comprising:
a bit boundary detection unit that detects a bit boundary signal from the received reception signal, the bit boundary signal indicating between which clocks a variation point of the reception signal is located among the N-phase clocks;
a clock update timing control unit that controls timings at which the sampling clock is updated;
a first bit boundary signal storage unit that stores the bit boundary signal at each of the timings;
a second bit boundary signal storage unit that takes in and stores a signal stored in the first bit boundary signal storage unit when a variation point of the reception signal is detected in the bit boundary detection unit, and does not update a signal stored therein when no variation point of the reception signal is detected; and
a first clock selection unit that selects the sampling clock based on a signal stored in the first bit boundary signal storage unit when a variation point of the reception signal is detected in the bit boundary detection unit, and selects the sampling clock based on a signal stored in the second bit boundary signal storage unit when no variation point of the reception signal is detected.
2. The communication device according to claim 1 , wherein the clock update timing control unit defines timing at which a predetermined number of bits are received in the payload as the timing at which the sampling clock is updated.
3. The communication device according to claim 1 , wherein
a frame of the reception signal has a structure in which the synchronous word is located at a head, and
the bit boundary detection unit detects a bit boundary signal of the synchronous word at a start of a reception of the frame and stores the detected bit boundary signal in the first bit boundary signal storage unit.
4. The communication device according to claim 1 , wherein the first clock selection unit comprises:
a first clock selection unit that selects the sampling clock based on a first bit boundary signal stored in the first bit boundary signal storage unit when a variation point of the reception signal is detected in the bit boundary detection unit; and
a second clock selection unit that selects the sampling clock based on a second bit boundary signal stored in the second bit boundary signal storage unit when no variation point of the reception signal is detected.
5. The communication device according to claim 4 , wherein
the first clock selection unit selects one clock that is away from a variation point of a reception signal indicated by the first bit boundary signal by a predetermined phase from the N-phase clocks, and
the second clock selection unit selects one clock that is away from a variation point of a reception signal indicated by the second bit boundary signal by a predetermined phase from the N-phase clocks.
6. The communication device according to claim 1 , wherein the bit boundary detection unit detects the bit boundary signal by comparing a reception signal received by using a clock having a first phase included in the N-phase clocks with the reception signal received by using a clock having a second phase adjacent to the first phase.
7. The communication device according to claim 1 , further comprising:
a synchronous detection unit that detects synchronization by performing reception using the N-phase clocks for the synchronous word and generates a clock identification signal used to identify a synchronously-detected clock; and
a second clock selection unit that selects the sampling clock based on the clock identification signal generated in the synchronous detection unit and the bit boundary signal detected in the bit boundary detection unit.
8. The communication device according to claim 7 , wherein the second clock selection unit selects one clock, which is a synchronously-detected clock indicated by the clock identification signal and is away from a variation point of a reception signal indicated by the bit boundary signal by a predetermined phase, from the N-phase clocks as the sampling clock.