There are two ways of setting up the card registers: The card uses two ring buffers to store packets: The card regularly scans all the transmit buffers looking for one it hasn’t sent, and then will transmit those it finds. If a new packet has been signalled then CSR0 bit 10 will be set. Personal tools Log in. You should also have a variable that stores the current ‘pointer’ into each buffer i. Once all the control registers are set up, you set bit 0 of CSR0, and then wait for initialization to be done.

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Select type of offense: The card uses two ring buffers to store packets: After you have properly handled an interrupt, you will need to write a 1 back to the appropriate bit in CSR0 or CSR4 before sending EOI to you interrupt controller or the interrupt will continue to be signalled. Flaming or offending other users. If you do not wish to use logical addressing the defaultthen set these bytes to zero.

If this is cleared, it means the driver ‘owns’ that particular ring buffer entry. During normal initialization and use of the cards, the CSRs are used exclusively. Sending packets involves simply ethhernet the packet details to the next available transmit buffer, ehernet flipping the ownership for the particular ring buffer entry to the card. The card regularly scans all the transmit buffers looking for one it hasn’t sent, and then will transmit those it finds.

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Thank You for Submitting Your Review,! The card maintains separate pointers internally. Sexually explicit or offensive language. Click here to review our site terms of use. If you believe this comment is offensive or violates the CNET’s Site Terms of Useyou can report it below this will not automatically remove the comment.


The next section will enable some interrupts on the card. This means that the index of the register you wish to access is first written to an index port, followed by either writing a new value to or reading the old value from a data register. You probably want this as it is far easier to poll for this situation which only occurs once anyway.

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And you may want to set bit 11 of CSR4 which automatically pads Ethernet packets which are too short to be at least 64 bytes. Each of these then contains a pointer to the actual physical address of the memory used for the packet.

At initialization, you would want the card to ‘own’ all the receive buffers so it can write new packets into them that it receives, then flip ownership to the driverand the driver to ‘own’ all the transmit buffers so it can write packets to be transmitted, then flip ownership to the driver.

To actually set up the card registers, we provide it with the address of our initialization structure by writing the low bits of its address to CSR1 and the high bits to CSR2. Ethwrnet that the MMIO access is sometimes absent on emulators or certain systems, this article will focus on the IO port access.

If a new packet has been signalled then CSR0 bit 10 will be set. There are other bits in CSR0 than can be set depending on how you set up interrupt masks in CSR3 and additionally other bits in CSR4 that can signal interrupts although these are usually masked out on reset.


Note that interrupts can come from many sources other than new packets.

Note that if you want to wait for an interrupt you will also need to set bit 6 of CSR0 or interrupts won’t be generated you will need to enable this anyway to get notification of received packets, so it makes sense to set it at the same time as the initialization bit. You can do this by either waiting for an interrupt if you didn’t disable the initialization done interrupt in CSR3 or by polling until CSR0 bit 8 is set.

Contents 1 Overview 2 Initialization and Register Access 2. If you want to keep the current one, you will need to first read it from the EPROM of the card it is exposed as the first 6 bytes of the IO space that the registers are in.

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See the spec description of CSR15 for further details. This article will pxnet on the Am79CA a. The posting of advertisements, profanity, or personal attacks is prohibited.

You also need a simple way of incrementing the pointer and wrapping back to the start if necessary. We will flesh out the interrupt handler later, but you should install the interrupt handler here as otherwise you will get crashes due to unhandled interrupts.