Bus system having improved control process
View Patent ↗The invention provides a bus system comprising a controller; a high speed data transfer bus, the data transfer bus being subject to one or more inherent physical-layer configuration constraints for proper electrical operation; and a separate control bus. Several devices are connected to the controller through the control bus and the data transfer bus. The controller is arranged to communicate with devices using the control bus in order to verify whether or not one or more of the physical-layer configuration constraints are satisfied. If such configuration constraints are not satisfied, the controller modifies the operation of some of the devices using control signals transmitted on the control bus in order to bring the data transfer bus to an operable condition. The invention makes it possible to use the bus system, even though physical-layer configuration constraints are violated. The invention applies to Rambus DRAM buses, where devices may be disabled to ensure respect of the constraint on the number of devices.
1. A bus system comprising a controller; a high speed data transfer bus, the data transfer bus being subject to one or more inherent physical-layer configuration constraints for proper electrical operation; and a separate control bus, said control bus and said data transfer bus connecting the controller and the, or each, device connected thereto, wherein the controller is arranged to communicate with devices using the control bus in order to verify whether or not one or more of the physical-layer configuration constraints are satisfied and, if such configuration constraints are not satisfied, to disable at least some of the devices using control signals transmitted on the control bus in order to bring the data transfer bus to an operable-condition.
2. The bus system of claim 1 wherein the controller is arranged to disable devices furthest from the controller on the data transfer bus.
3. The bus system of claim 1 wherein, if said configuration constraints are not satisfied, the controller is arranged to set a stored indicator indicative of a error condition.
4. The bus system of claim 1 wherein said physical-layer constraints comprise a constraint on the number of devices connected to the bus.
5. A computer comprising a bus according to claim 1 .
6. In a bus system comprising a controller; a high speed data transfer bus, the data transfer bus being subject to one or more inherent physical-layer configuration constraints for proper electrical operation; and a separate control bus, said control bus and said data transfer bus connecting the controller and the, or each, device connected thereto, a process for bringing the data transfer bus to an operable condition, comprising the steps of communicating with devices using the control bus in order to verify whether or not one or more of the physical-layer configuration constraints are satisfied and, if such configuration constraints are not satisfied, disabling at least some of the devices using control signals transmitted on the control bus.
7. The process of claim 6 wherein said step of modifying comprises disabling devices furthest from the controller on the data transfer bus.
8. The process of claim 6 further comprising, if said configuration constraints are not satisfied, setting a stored indicator indicative of a error condition.
9. The process of claim 6 , wherein said physical-layer constraints comprise a constraint on the number of devices connected to the bus.
10. A computer program product for a computer with a bus system comprising a controller; a high speed data transfer bus, the data transfer bus being subject to one or more inherent physical-layer configuration constraints for proper electrical operation; and a separate control bus, said control bus and said data transfer bus connecting the controller and the, or each, device connected thereto, said computer program product comprising a computer readable medium having thereon: computer program code means, when said program is loaded, to make the controller communicate with devices using the control bus in order to verify whether or not one or more of the physical-layer configuration constraints are satisfied and, if such configuration constraints are not satisfied, to make the controller disable at least some of the devices using control signals transmitted on the control bus.
11. The computer program product of claim 10 wherein, if such configuration constraints are not satisfied, the computer program code means make the controller disable devices furthest from the controller on the data transfer bus.
12. The computer program product of claim 10 wherein, if such configuration constraints are not satisfied, the computer program code means set a stored indicator indicative of a error condition.
13. The computer program product of claim 10 wherein said physical-layer constraints comprise a constraint on the number of devices connected to the bus.