You can easily develop an AX driver based on the standard NE driver source code with a couple of minor modifications. Be the first to write a review. This item will be posted through the Global Shipping Program and includes international tracking. Report item — opens in a new window or tab.

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If neither are reached, the DMA is allowed to use the next buffer. Thus, the packets previously received and still contained in the Ring will not be destroyed. In a heavily loaded network environment the local DMA may be disabled, preventing the AX from buffering packets from the network. The following procedure is required to recover from a Receiver Buffer Ring Overflow.

If this routine is not adhered to, the AX may act in an unpredictable manner. It should also be noted that it is not permissible to service an overflow interrupt by continuing to empty packets from the receive buffer without implementing the prescribed overflow routine. Wait for at least 1. Since the AX will complete any transmission or reception that is in progress, it is necessary to time out for the maximum possible duration of an Ethernet transmission or reception.

By waiting 1. Previously, it was recommended that the RST bit of the Interrupt Status Register be polled to insure that the pending transmission or reception is completed. This bit is not a reliable indicator and subsequently should be ignored. Read the stored value of the TXP bit from step 1, above. This step determines if there was a transmission in progress when the stop command was issued in step 2. If neither the PTX nor TXE bit was set, then the packet will essentially be lost and retransmitted only after a time-out takes place in the upper level software.

By determining that the packet was lost at the driver level, a transmit command can be reissued to the AX once the overflow routine is completed as in step Also, it is possible for the AX to defer indefinitely, when it is stopped on a busy network.

Step 5 also alleviates this problem. Step 5 is essential and should not be omitted from the overflow routine, in order for the AX to operate correctly. Place the AX in mode 1 loopback. This can be accomplished by writing 22H to the Command Register.

Remove one or more packets from the receive bufferring. Take the AX out of loopback. This is done by writing the Transmit Configuration Register with the value it contains during normal operation. Bits D2 and D1 should both be programmed to 0. This is done by writing a value of 26H to the Command Register.


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