US 6,311,245 B1Granted

Method for time multiplexing a low-speed and a high-speed bus over shared signal lines of a physical bus

AssigneeMicron Technology, Inc.

InventorDean A. Klein

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Abstract

A method for combining a low-speed communications bus and a high-speed communications bus into a single multiplexed communications bus that supports both low-speed and high-speed operations. The multiplexed communications bus contains a low-speed state machine and a high-speed state machine. The multiplexed communications bus is controlled by the low-speed state machine and operated at low speed in order to conduct transactions between two low-speed peripheral devices, and is controlled by the high-speed state machine and operated at high speed in order to conduct transactions between and two high-speed peripheral devices. For transactions between peripheral devices having different speeds, either a buffer is used to store data between data transmission and data reception by the two devices, or the low-speed and high-speed state machines are synchronized and operationally interleaved.

Claims38

Dependent claims

A method of communicating between a central communications device, a high-speed device and a plurality of low-speed devices, comprising:

communicating between the central communications device and the high-speed device and between the central communications device and each of the low-speed devices through a set of bus lines that are shared by the high-speed device and the low-speed device;
communicating between the central communications device and the high-speed device through a set of high-speed bus lines and between the central communications device and each of the low-speed devices through a set of low-speed bus lines, the low-speed lines being separate from the high-speed lines;
communicating between a first and a second of the low-speed devices by the first low-speed device initiating a bus operation with the second low-speed device, and using the shared bus lines and the low-speed set of bus lines to carry out the bus operation;
and
communicating between one of the low-speed devices and the high-speed device by initiating a bus operation as follows:
when the low-speed device transmits data as part of the bus operation, transmitting the data to the central communications device using the shared bus lines and the low-speed set of bus lines;
when the high-speed device transmits data as part of the bus operation, transmitting the data to the central communications device using the shared bus lines and the high-speed set of bus lines;
when the low-speed device receives data as part of the bus operation, transmitting the data from the central communications device to the low-speed device using the shared bus lines and the low-speed set of bus lines;
and
when the high-speed device receives data as part of the bus operation, transmitting the data from the central communications device to the high-speed device using the shared bus lines and the high-speed set of bus lines.

7 more elements

A method of communicating between a system controller, a plurality of high-speed devices and a plurality of low-speed devices, the high-speed and low-speed devices being coupled to the system controller through a bus having a plurality of bus lines, the method comprising:

communicating at a high rate of speed between the system controller and each of the high-speed devices through a first set of the bus lines and a second set of the bus lines, the bus lines in the first set being different from the bus lines in the second set;
and
communicating at a low rate of speed between the system controller and each of the low-speed devices through the first set of the bus lines and a third set of the bus lines, the bus lines in the third set being different from the bus lines in the first set and the bus lines in the second set;
communicating between a first and a second of the low-speed devices by the first low-speed device initiating a bus operation with the second low-speed device, and using the first set and third set of bus lines at low speed to carry out the bus operation;
communicating between a first and a second of the high-speed devices by the first high-speed device initiating a bus operation with the second high-speed device using the first set and second set of bus lines at high speed to carry out the bus operation;
and
communicating between one of the low-speed devices and one of the high-speed devices by initiating a bus operation as follows:
when the low-speed device transmits data as part of the bus operation, transmitting the data to the system controller using the first set and the third set of bus lines;
when the high-speed device transmits data as part of the bus operation, transmitting the data to the system controller using the first set and the second set of bus lines;
when the low-speed device receives data as part of the bus operation, transmitting the data from the system controller to the low-speed device using the first set and the third set of bus lines;
and
when the high-speed device receives data as part of the bus operation, transmitting the data from the system controller to the high-speed device using the first set and the second set of bus lines.

9 more elements

A method for time multiplexing a low-speed communications bus and a high-speed communications bus on a single physical communications bus, the method comprising:

connecting at least one low-speed device to the physical communications bus;
connecting at least one high-speed device to the physical communications bus;
when a low-speed device initiates a bus operation with another low-speed device, operating the physical communications bus at low speed to carry out the bus operation;
when a high-speed device initiates a bus operation with another high-speed device, operating the physical communications bus at high speed to carry out the bus operation;
and
when a bus operation between a low-speed and a high-speed device is initiated,
operating the physical communications bus at the speed required by the device that transmits data for the operation,
transmitting the data to the physical communications bus by the device that transmits data for the operation,
operating the physical communications at the speed required by the device that receives data as a result of the bus operation, and
receiving the data transmitted to the bus by the device that receives data as a result of the bus operation.

7 more elements

A method for increasing the reliability and decreasing the cost of a system controller by decreasing the pin connectors required on the system controller to support bus connections to buses that connect the system controller to peripheral devices in a computer system, each bus comprising signal lines, an arbiter, and a state machine, the method comprising:

combining multiple buses into a single physical bus that contains less signal lines and correspondingly requires less pin connectors than the sum of the signal lines contained in and pin connectors required by the multiple buses, the single physical bus having an arbiter and one or more state machines;
and
connecting the system controller and the peripheral devices to the single physical bus;
detecting a speed of a peripheral device that initiates a bus operation by the arbiter;
when a low-speed peripheral device initiates a bus operation with another low-speed peripheral device, activating the low-speed state machine to control operation of the physical bus at low speed to carry out the bus operation;
when a high-speed peripheral device initiates a bus operation with another high-speed peripheral device, activating the high-speed state machine to control operation of the physical bus at high speed to carry out the bus operation;
and
when a bus operation between a low-speed and a high-speed peripheral device is initiated,
activating the state machine corresponding in speed to the peripheral device that transmits data for the operation in order to operate the physical bus at the speed required by the peripheral device that transmits data for the operation,
transmitting the data to the physical bus by the peripheral device that transmits data for the operation,
activating the state machine corresponding in speed to the peripheral device that receives data as a result of the bus operation in order to operate the physical bus at the speed required by the peripheral device that receives data as a result of the bus operation, and
receiving the data transmitted to the physical bus by the peripheral device that receives data as a result of the bus operation.

9 more elements

Dependencies are inferred from the claim text.