Apparatus and method for topography dependent signaling

Claims

What is claimed is:

1. A method in a bus system of adjusting a transmission parameter of a transmitter in the bus system, comprising:

determining a topography of the bus system;

determining a control value based upon the topography;

conveying the control value to the transmitter; and

adjusting the transmission parameter of the transmitter using the control value;

wherein the topography of the bus system indicates a distance of a module including the transmitter from a receiver.

2. The method of claim 1 wherein the transmission parameter is a slew rate.

3. The method of claim 1 wherein the topography of the bus system is one of a preestablished set of bus topographies.

4. The method of claim 1 wherein determining the topography of the bus system includes reading device configuration information from a module including the transmitter.

5. The method of claim 1 wherein the transmission parameter is an output current magnitude.

6. The method of claim 1 wherein the transmission parameter is an output voltage asymmetry.

7. The method of claim 1 wherein the transmission parameter is a slew rate.

8. The method of claim 1 wherein the transmission parameter is an output current magnitude.

9. The method of claim 1 wherein the transmission parameter is an output voltage asymmetry.

10. A method in a bus system of adjusting a transmission parameter of a transmitter in the bus system, comprising:

determining a topography of the bus system;

determining a control value based upon the topography;

conveying the control value to the transmitter; and

adjusting the transmission parameter of the transmitter using the control value;

wherein determining the topography of the bus system includes reading device configuration information from a module including the transmitter.

11. The method of claim 10 wherein the topography of the bus system is one of a preestablished set of bus topographies.

12. A method in a bus system of adjusting a transmission parameter of a transmitter located on a first module of a plurality of modules in the bus system, comprising:

determining a position of the first module within the bus system;

determining a control value based upon the position of the first module;

conveying the control value to the transmitter; and

adjusting the transmission parameter of the transmitter using the control value.

13. The method of claim 12 wherein the transmission parameter is a slew rate.

14. The method of claim 12 wherein determining the position of the first module includes reading a module library associated with the first module.

15. The method of claim 12 wherein the transmission parameter is an output current magnitude.

16. The method of claim 12 wherein the transmission parameter is an output voltage asymmetry.

17. A signal transmission bus system, comprising:

a port for receiving bus system topography information;

a register coupled to the port, the register storing the bus system topography information;

parameter adjustment circuitry coupled to the register adjusting a parameter control signal in accordance with the bus system topography information; and

an output driver for driving an output signal onto a bus within the bus system, the output driver setting a transmission parameter of the output signal in accordance with the parameter control signal.

18. The apparatus of claim 17 wherein the transmission parameter is a one of a slew rate, output current magnitude, and output voltage asymmetry.

19. The apparatus of claim 17 wherein the bus system topography information includes information corresponding to a bus position of a device that includes the output driver.

20. The apparatus of claim 17 wherein the output driver is in a device that is included in a module that also includes other devices having output drivers, and the bus system topography information includes a information corresponding to a bus position of the module.

21. Apparatus for adjusting a slew rate of an output signal generated by a transmitter, comprising:

a port for receiving position dependent information associated with the transmitter;

a register for storing the position dependent information;

slew rate control circuitry coupled to the register for adjusting a slew rate control signal in accordance with the position dependent information; and

output circuitry for driving the output signal onto a bus coupling the transmitter to a receiver, the output driver setting the slew of the output signal in accordance with the slew rate control signal.

22. The apparatus of claim 21 wherein the output circuitry comprises:

an output multiplexer responsive to the slew rate control signal for generating a clocked data signal with a slew rate corresponding the slew rate control signal; and

an output current driver receiving the clocked data signal and generating the output signal.

23. Apparatus for adjusting an output current of an output signal generated by a transmitter, comprising:

a port for receiving position dependent information associated with the transmitter;

a register for storing the position dependent information;

current control circuitry coupled to the register for adjusting a current control signal in accordance with the position dependent information; and

output circuitry for driving the output signal onto a bus coupling the transmitter to a receiver, the output driver setting a magnitude of the current of the output signal in accordance with the current control signal.

24. The apparatus of claim 23 wherein the current control circuitry comprises:

a comparator having a first input, a second input and a comparator output, the first input being coupled to a reference voltage and the second input being coupled to a first voltage having a level determined in response to the position dependent information, the comparator generating an up/down signal on the comparator output in accordance with the first and second inputs; and

a counter, coupled to the output of the comparator, generating the current control signal in response to the up/down signal.

25. The apparatus of claim 24 wherein the apparatus further comprises:

a multiplexer driving the first voltage onto a multiplexer output, the multiplexer selecting one of a plurality on input voltages as the first voltage in response to the position dependent information, and wherein the plurality of input voltages are generated from a current generated in accordance with the current control signal.

26. A system with adjustable signal characteristics, comprising:

a bus;

a controller coupled to the bus for determining a topography dependent parameter associated with a particular transmitter and for transmitting the topography dependent parameter to the particular transmitter;

a plurality of modules coupled to the bus, each module including:

a topography indicating circuit coupled to the controller via the bus, the topography indicating circuit indicating a topography of each transmitter on the bus; and

a plurality of devices, each device including a bus transmitter for transmitting data to the controller via the bus;

each bus transmitter including:

a port for receiving a first topography dependent parameter;

a first register coupled to the port, the first register storing the first topography dependent parameter;

a first parameter adjustment circuit coupled to the first register adjusting a first parameter control signal in accordance with the first topography dependent parameter; and

an output driver for driving a first data signal onto the bus, the output driver setting a transmission parameter of the first data signal in accordance with the first parameter control signal.

27. The system of claim 26 wherein the topography dependent parameter is a slew rate.

28. The system of claim 26 wherein each module in the plurality of modules has an associated topography that is one of a preestablished set of bus topographies.

29. The system of claim 26 wherein the topography of each module corresponds to a distance between a receiver and the module.

30. The system of claim 26 wherein each device further comprises a bus receiver receiving data via the bus from the controller, each bus receiver including:

a second register storing a second topography dependent parameter;

a second parameter adjustment circuit coupled to the second register adjusting a second parameter control signal in accordance with the second topography dependent parameter; and

an input buffer receiving a second data signal from the bus, the input buffer generating a third signal from the second data signal, the input buffer adjusting a parameter of the third signal in accordance with the second parameter control signal.

31. The system of claim 30, wherein the parameter of the third signal that is adjusted in accordance with the second control signal is a receiving timing parameter.

32. The system of claim 30, wherein the parameter of the third signal that is adjusted in accordance with the second control signal is a threshold voltage parameter.

33. The system of claim 26 wherein the topography dependent parameter is an output current magnitude.

34. The system of claim 26 wherein the topography dependent parameter is an output voltage asymmetry.

35. A method in a bus system of adjusting a parameter of a bus receiver in the bus system, comprising:

determining a topography of the bus system;

determining a control value based upon the topography;

conveying the control value to the bus receiver; and

receiving an input signal from a bus coupling the bus receiver to a transmitter, and generating a first signal from the input signal, including adjusting a parameter of the first signal in accordance with the control value;

wherein the topography of the bus system indicates a distance of a module including the bus receiver from the transmitter.

36. The method of claim 35 wherein the topography of the bus system is one of a preestablished set of bus topographies.

37. The method of claim 35, wherein the parameter of the first signal that is adjusted in accordance with the control value is a receiving timing parameter.

38. The method of claim 35, wherein the parameter of the first signal that is adjusted in accordance with the control value is a threshold voltage parameter.

39. The method of claim 35 wherein determining the topography of the bus system includes reading device configuration information from a module including the bus receiver.

40. A method in a bus system of adjusting a parameter of a bus receiver in the bus system, comprising:

determining a topography of the bus system;

determining a control value based upon the topography;

conveying the control value to the bus receiver; and

receiving an input signal from a bus coupling the bus receiver to a transmitter, and generating a first signal from the input signal, including adjusting a parameter of the first signal in accordance with the control value;

wherein determining the topography of the bus system includes reading device configuration information from a module including the bus receiver.

41. The method of claim 40 wherein the topography of the bus system is one of a preestablished set of bus topographies.

42. The method of claim 40, wherein the parameter of the first signal that is adjusted in accordance with the control value is a receiving timing parameter.

43. The method of claim 40, wherein the parameter of the first signal that is adjusted in accordance with the control value is a threshold voltage parameter.

44. A method in a bus system of adjusting a receive data parameter of a bus receiver located on a first module of a plurality of modules in the bus system, comprising:

determining a position of the first module within the bus system;

determining a control value based upon the position of the first module;

conveying the control value to the bus receiver; and

adjusting the receive data parameter of the bus receiver using the control value.

45. The method of claim 44 wherein the receive data parameter is a temporal equalization parameter.

46. The method of claim 44 wherein determining the position of the first module includes reading a module library associated with a module including the bus receiver.

47. A signal transmission bus system, comprising:

a port for receiving bus system topography information;

a register coupled to the port, the register storing the bus system topography information;

parameter adjustment circuitry coupled to the register adjusting a parameter control signal in accordance with the bus system topography information; and

a bus receiver receiving an input signal from a bus coupling the bus receiver to a transmitter, the bus receiver generating a first signal from the input signal, including adjustment circuitry for adjusting a parameter of the first signal in accordance with the parameter control signal.

48. The system of claim 42 wherein the parameter is a temporal equalization parameter.

49. The system of claim 47, wherein the parameter of the first signal that is adjusted in accordance with the parameter control signal is a receiving timing parameter.

50. The system of claim 47, wherein the parameter of the first signal that is adjusted in accordance with the parameter control signal is a threshold voltage parameter.