MAC Control/Status

MAC Control/Status

This command provides a host driver with two distinct levels of service to an Ethernet port located on the 4221.

First, it provides a general mechanism to control the Ethernet port, without the driver having to know any particulars about the actual Ethernet interface chip being used. Drivers written for long-term portability should use these features.

Second, it provides a transparent access to certain useful capabilities provided by the actual Ethernet interface chip, which could be quite useful in specialized applications like diagnostic programs, network monitor programs, custom point-to-point applications, or for tuning for specialized network application environment. Since these capabilities are intimately associated with a particular Ethernet interface chip, drivers using these will, by definition, not be as portable to future versions of this host-interface on controller using a different chip.

Most of these operations are only permitted on a port that has been disabled. Normally, the host will disable the port, change the operating parameters, and then enable the port, which activates it with the new operational characteristics. This means that the host may have to submit a number of MAC Control IOPBs sequentially in order to perform complex configurations on ports.

In order to disable a port, issue the MAC Control IOPB with the SM bit set in the Command Options field, and the MAC Options field set to zero.

Please note that various error are returned if illegal combinations of options are specified, or the port is in the wrong state to perform a particular action. Normally, there will be additional information printed to the controller console when each of these errors occurs.

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