Printed circuit board, and backplane data transmission method
In a receiving-side printed circuit board, a reflected-waveform analyzing unit analyzes a reflected wave generated in a transmission line on a backplane along with transmission of a signal from a transmitting-side printed circuit board, and acquires waveform data that indicates a waveform of the reflected wave. An input signal identifying unit calculates a size of the reflected wave that is currently received based on the waveform data and data on previously received signals. The input signal identifying unit corrects a threshold value by the calculated size, and identifies a state of a bit indicated by the signal from the transmitting-side printed circuit board.
1. A printed circuit board on a backplane that exchanges signals with another printed circuit board on the backplane via a transmission line, the printed circuit board comprising:
an analyzing unit that analyzes a reflected wave generated in the transmission line along with transmission of a signal from the other printed circuit board and obtains waveform data that indicates a waveform of the reflected wave;
a calculating unit that calculates a size of the reflected wave based on the waveform data and data on previously received signals; and
an identifying unit that corrects a threshold value by calculated size of the reflected wave and identifies a state of a bit indicated by the signal from the other printed circuit board.
2. The printed circuit board according to claim 1 , wherein the analyzing unit analyzes the reflected wave upon the other printed circuit board being mounted on the backplane.
3. The printed circuit board according to claim 1 , wherein the analyzing unit analyzes the reflected wave before starting exchange of data with the other printed circuit board via the transmission line.
4. The printed circuit board according to claim 1 , wherein the identifying unit includes a plurality of identifying units that identify the state of the bit based on a predetermined threshold value uniquely assigned to each of the identifying units, the printed circuit board further comprising:
a selector that selects, as an authentic state of the bit, the state of the bit identified by one of the identifying units assigned a threshold value corresponding to the calculated size of the reflected wave.
5. A backplane data transmission method for exchange of signals between a first printed circuit board and a second printed circuit board via transmission line on a backplane, the backplane data transmission method comprising:
the first printed circuit board transmitting a signal of a single waveform to the second printed circuit board via the transmission line;
the second printed circuit board analyzing a reflected wave generated in the transmission line along with the transmission of the signal to obtain waveform data that indicates a waveform of the reflected wave;
the second printed circuit board calculating a size of the reflected wave based on the waveform data and data on previously received signals;
the second printed circuit board correcting a threshold value by calculated size of the reflected wave; and
the second printed circuit board identifying a state of a bit indicated by the signal transmitted from the first printed circuit board.