Method and apparatus for controlling data flow through an ATM interface

A state machine associated with a channel for controlling a flow of data for said channel from a host computer to an ATM network, the state machine having:

• a scheduled state in which
• data to be sent on said channel is copied from the host computer into a local buffer;
• and
• cells for said channel are not constructed from data stored in the local buffer;
• a data available state in which cells for said channel are constructed from data stored in said local buffer and transmitted onto said ATM network;
• said state machine being configured to move from said scheduled state to said data available state when said local buffer contains an amount of data for said channel that exceeds a first predetermined threshold;
• and
• a segmentation state in which
• data to be sent on said channel is not copied from the host computer into said local buffer;
• and
• cells for said channel are constructed from data stored in said local buffer and transmitted onto said ATM network;
• said state machine being configured to move from said data available state to said segmentation state when all of the data in said host computer that is to be sent on said channel has been copied into said local buffer.

A method for controlling a flow of data for a channel from a host computer to an ATM network, the method comprising the steps of:

• causing a state machine to move from a scheduled state to a data available state when a local buffer contains an amount of data for said channel that exceeds a first predetermined threshold;
• if said state machine is in said scheduled state, then performing the step of
• copying data to be sent on said channel from the host computer into said local buffer;
• and
• if said state machine is in said data available state, then performing the steps of
• constructing cells for said channel from data stored in said local buffer;
• and
• transmitting said cells onto said ATM network;
• and
• causing said state machine to move from said data available state to a segmentation state when all of the data in said host commuter that is to be sent on said channel has been copied into said local buffer;
• if said state machine is in said segmentation state, then performing the steps of
• ceasing to copy data to be sent on said channel from the host computer into said local buffer;
• and
• continuing to construct cells for said channel from data stored in said local buffer and transmitted onto said ATM network.

A state machine associated with a channel for controlling a flow of data for said channel from a host computer to an ATM network, the state machine having a plurality of states, said state machine being configured to move from a current state to a next state of said plurality of states when each of the following occurs:

• an operation is scheduled for transferring data for said channel from said host computer to a local buffer;
• said host computer indicates that data for said channel is ready to be transferred from said host computer to said local buffer;
• all of the data in said host computer that is to be sent on said channel has been copied into said local buffer;
• a portion of said local buffer that is allocated for said channel becomes full before all of the data in said host computer that is to be sent on said channel has been copied into said local buffer;
• said local buffer contains an amount of data for said channel that exceeds a first predetermined threshold;
• and
• said local buffer contains an amount of data for said channel that falls below a second predetermined threshold.

A computer system configured to communicate over a network, the computer system comprising:

• a host memory;
• a system bus coupled to said host memory;
• and
• a network interface coupled to said system bus for controlling a flow of data between the host memory and the network, the network interface comprising:
• a local buffer for storing data to be transmitted onto said network;
• a timer that corresponds to a channel, the timer being configured to generate cell transmit requests;
• a channel flow controller coupled to said timer, said channel flow controller configured to generate an enable signal associated with said channel when said local buffer contains at least a first amount of data for said channel;
• a segmentation unit coupled to said timer, said channel flow controller and said local buffer, said segmentation unit configured to respond to said cell transmit requests from said timer if and only if said channel flow controller is generating said enable signal, said segmentation unit configured to read data from said local buffer and to transmit said data in cells onto said network on said channel in response to said cell transmit requests from said timer.