Cross talk suppression in a bidirectional bus
First Claim
1. A multiple line bus, comprising:
- a first line driven by a pair of drivers;
a first pair of active impedance elements connected between the first line and a second line of the bus;
a second pair of active impedance elements connected between the first line and a third line of the bus;
further comprising a current source connected between a first driver of the pair of drivers and the second line, wherein the current source is configured to generate a current that offsets a current induced in the second line when the first driver drives the first line.
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Abstract
A bidirectional bus and data processing system suitable for suppressing cross talk noise are disclosed. The bidirectional bus includes, a first interconnect line driven by a pair of drivers, a first pair of impedance elements connected between the first line and a second line of the bus, and a second pair of impedance elements connected between the first line and a third line of the bus. In one embodiment, the capacitive coupling per unit length between the first line and the second line is approximately equal to k and the impedance of the first pair of impedance elements is approximately equal to (υk)−1, where υ is the speed of light through a dielectric in which the first and second lines are located. In one embodiment, the impedance of the first driver is approximately equal to (υc0)−1, wherein c0 is the self-capacitance of the first line.
15 Citations
22 Claims
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1. A multiple line bus, comprising:
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a first line driven by a pair of drivers;
a first pair of active impedance elements connected between the first line and a second line of the bus;
a second pair of active impedance elements connected between the first line and a third line of the bus;
further comprising a current source connected between a first driver of the pair of drivers and the second line, wherein the current source is configured to generate a current that offsets a current induced in the second line when the first driver drives the first line. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A bidirectional data bus for connecting a processor and a system memory of a data processing system, comprising:
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a first line driven by a pair of drivers;
a first pair of impedance elements connected between the first line and a second line of the bus;
a second pair of impedance elements connected between the first line and a third line of the bus;
wherein the impedance of each of the drivers is approximately equal to (υ
c0)−
1, wherein c0 is the self-capacitance of the first line and υ
is the speed of light through a dielectric in which the lines are embedded.- View Dependent Claims (16, 17, 18)
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15. The data bus of claim wherein the capacitive coupling per unit length between the first line and the second line is approximately equal to k and the impedance of the first pair of impedance elements is approximately equal to (υ
- k)−
1, where υ
is the speed of light through a dielectric in which the first and second lines are located.
- k)−
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19. A method suppressing cross talk in a bidirectional bus, comprising:
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driving a first line of the bus with a first signal by a first driver wherein the first driver produces a current I in the first line; and
, responsive thereto;
drawing a current J from a second line adjacent to the first line with a current source, wherein J/I is approximately equal to k/c, k is the capacitive coupling per unit length between the first and second lines, and c is approximately c0+2k, where c0 is the self-capacitance of the first line; and
terminating the first line with an impedance element between the first and second lines, wherein the impedance of the impedance element is approximately equal to (υ
k)−
1 wherein k is the capacitive coupling per unit length between the first and second lines and υ
is the speed of light in a dielectric in which the first and second lines are located.- View Dependent Claims (20, 21, 22)
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Specification