Network Cards

ID #3924

Commodore: A2060

Connection: Zorro II

a2060_1_sm.jpg

Hi Res Version - 926K

TypeARCnet (Attached Resource Computer NETwork)
Coax & BNC:Yes
UTP & RJ45:No
SANA-II Driver: Yes
MNI Driver: No
Other Driver: Yes (AS255r TCP/IP stack has built-in support)

The A2060 is a full length Zorro-II network card. The A2060 is NOT an Ethernet card, it uses a different networking standard called ARCnet. Arcnet was a popular network standard during the 1980's but has been pretty much killed off by Ethernet, except for industrial and embedded applications where it's more robust than ethernet and ARCnet is a token ring (not to be confused with IBM's Token Ring) networking standard which can be arranged in a bus topology or a star topology in both Coaxial Cabling and UTP. Whilst the cabling may be very similar to Ethernet cabling, it is different electrically. ArcNet requires RG62/93 Ohm and NOT RG58/50 Ohm which ethernet uses. It is also available in a range of speeds from 150Kb/s to 10Mb/s. The A2060 is capable of transferring at about 150K/sec and uses 2.5Mbit ARCnet. The A2060 has several common bugs. Firstly, the "hybrid" chip that forms the electronic interface to the ARCnet network comes in two different versions: HYC 9058 (for bus networks) and HYC 9068 (for star networks). As the A2060 manual describes it, the board is for a bus network, but many A2060s come with the 9068 (star) hybrid installed. A bus network needs 93-ohm terminators at each end, and this works fine with the 9058 (bus) version of the hybrid. With the 9068, however, the hybrid itself performs the termination. To connect two machines with 9068 hybrids, run coax from one machine to the other, without using terminators. Using T-connectors to attach more machines in the middle of the bus may or may not work, due to each one adding its termination to the bus. To connect a 9068-version A2060 to a bus network of 9058-version A2060s, place it at the end of the chain and connect the cable directly, without a terminator (this may limit the network to only being operational when the 9068-equipped machine is on). Both versions of the card should have no problems when attached directly to an active hub. It is also possible to replace the HYC 9068 hybrid with the 9058 version, provided you can locate one. There are also several well-known problems with version 37.2 of the "a2060.device" driver software. Replacements for this driver are available in the comm/net directory of Aminet. Some commercial networking packages like Envoy 2.0 also include much better replacement drivers. If the A2060 does not perform reliably even with updated driver software, check the board for cold solder joints on hand-soldered components like the BNC coax connector and DIP switches. Some or all of these components may need to have overly-long leads trimmed to prevent interference with adjacent cards or connectors. Finally, the Arcnet address switches on the back of the board are labelled incorrectly in the manual (or on the board, depending on how you look at it). At least some A2060's have a sticker stuck onto the DIP switch, which may disagree with both other references. Ignore all of these: the correct layout is described in the Switches section below. (Assign Arcnet ID numbers starting with 254 and decreasing from there. This will provide a slight performance increase due to Arcnet's token-passing setup.)

Board Layout

  _________________________________________________________________
 |        _________                 ...                            |___
 |       |   ROM   |                LED                            |
 |       |_________|                                 ______        |
 |                                                  |      |       |
 |                                                  |      |   Bit0#
 |                                                  |Hybrid|    .  # Arcnet
 |                                                  |      |    .  # Node ID
 |                       (Hybrid version number is  |      |    .  # Switches
 |                        labelled on the back side |      |   Bit7#
 |                        of the potted "chip.")    |______|       |_
 |                                                                 |_| BNC
 |                                                                 |
 |_________________________________________________________________|
     |||||||||||||||||||||||||||                                   |
 

Jumpers

    LED: Access LED. Attach a hard disk access LED here to see activity on
         the Arcnet bus. The left pin of the connector is positive, and the
         board provides a current-limiting resistor.

Switches

    Arcnet Node ID: This switch is used to set the Arcnet address of the
      board (refer to the board diagram above). Bit 0 is the switch farthest
      from the BNC connector; bit 7 is the closest to the BNC connector.

    Switch settings:

      1: Down (toward the solder side of the board)
      0: Up   (toward the component side of the board)

    Note: Zero is reserved, and not a valid Arcnet address.

  Example Arcnet Node Address Settings

     ID     Binary   Bit7  Bit6  Bit5  Bit4  Bit3  Bit2  Bit1  Bit0
    -----  --------  ----  ----  ----  ----  ----  ----  ----  ----
     254   11111110  down  down  down  down  down  down  down   up

     253   11111101  down  down  down  down  down  down   up   down

     252   11111100  down  down  down  down  down  down   up    up

     128   10000000  down   up    up    up    up    up    up    up

       3   00000011   up    up    up    up    up    up   down  down

       2   00000010   up    up    up    up    up    up   down   up

       1   00000001   up    up    up    up    up    up    up   down

The card does have other known problems. When it it is accessed continuously such as when a file is being transfered the voltage in the area of the LED connector drops below 5V to less than 3V (these can get even worse if an LED is connected). The dropping voltage stops the buffers from supplying the correct byte and instead the last accessed byte is repeated which leads to lots of timeouts, unknown packets etc. To fix it requires removing the small capacitor close to the LED connector (5V 2.2uF) and soldering an extra wire from the 5V and the GND to the IC (74Ls244) close to the LED connector.

Contributions to this page by:
Greg Scott (National Amiga), Iggy Drougge, RiWa & Friends, Warren Block

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Last update: 2009-01-26 21:23
Revision: 1.0

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