System and method for low-overhead monitoring of transmit queue empty status

A system for sending data, said system comprising:

• a host processor including a host processor memory that stores copies of data packets;
• and
• a transmit device coupled to said host processor that receives, stores, and transmits said data packets, said transmit device including,
• a transmit device memory that stores said data packets until said data packets are transmitted, and
• a state machine coupled to said transmit device memory that monitors for when said transmit device memory receives and transmits said data packets to determine when an interrupt should be sent to said host processor to clear said copies of said data packets from said host processor memory.

A method of monitoring a queue in a transmit device of a communications network, said method comprising the steps of:

• a) storing data packets in a host processor queue;
• b) sending said data packets to said queue in said transmit device causing said queue in said transmit device to transition to a not-empty state;
• c) monitoring said queue in said transmit device to determine when said queue transitions from said not-empty state back to an empty state;
• d) starting a counter when said queue transitions from said not-empty state to said empty state;
• and
• e) generating an interrupt signal when a counter value in said counter reaches a threshold value.

A method of monitoring queue status, comprising the steps of:

• detecting when a queue has changed from an empty state to a not-empty state;
• starting a watchdog counter when said queue transitions back to said empty state;
• and
• generating an interrupt signal when said watchdog counter equals a watchdog value.

A method for reducing overhead in a host controller comprising the steps of:

• receiving first data at a host controller;
• storing said first data in said host queue;
• copying said first data to a transmitter queue;
• receiving second data at said host controller;
• determining whether said host queue is full;
• if said host queue is full, determining whether said first data has been transmitted from said transmitter queue;
• and
• if said first data was transmitted, clearing said first data from said host queue and storing said second data in said host queue.