GD82559ER — Networkin g Silicon
operate independently. Control is switched between the two units according to the microcode instruction flow. The independence of the Receive and Command units in the micromachine allows the 82559ER to interleave commands and receive incoming frames, with no
The 82559ER contains an interface to an external Flash memory, and external serial EEPROM. These two interfaces are multiplexed. The Flash interface, which could also be used to connect to any standard
The 82559ER FIFO subsystem consists of a 3 Kbyte transmit FIFO and 3 Kbyte receive FIFO. Each FIFO is unidirectional and independent of the other. The FIFO subsystem serves as the interface between the 82559ER parallel side and the serial CSMA/CD unit. It provides a temporary buffer storage area for frames as they are either being received or transmitted by the 82559ER, which improves performance:
•Transmit frames can be queued within the transmit FIFO, allowing
•The storage area in the FIFO allows the 82559ER to withstand long PCI bus latencies without losing incoming data or corrupting outgoing data.
•The 82559ER transmit FIFO threshold allows the transmit start threshold to be tuned to eliminate underruns while concurrent transmits are being performed (i.e. pending transmits will not be affected by the change in FIFO threshold).
•The FIFO subsection allows extended PCI burst accesses with zero wait states to or from the 82559ER for both transmit and receive frames. This is because such the transfer is to the FIFO storage area, rather than directly to the serial link.
•Transmissions resulting in errors (collision detection or data underrun) are retransmitted directly from the 82559ER FIFO, therey increasing performance and eliminating the need to
•Incoming runt receive frames (frames that are less than the legal minimum frame size) can be discarded automatically by the 82559ER without transferring this faulty data to the host system, and without host intervention.
•Bad Frames resolution can be selectively left to the 82559ER, or under software control.
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