Controller Initialization Block (CIB)

Special Network Options

Originally, this field allowed the host to set several network related options, such as disabling receives, or disabling transmit CRC. A multiport controller requires that this type of control be associated with a particular port, rather than as a global configuration parameter, so these types of functions have been moved to the MAC Control IOPB. However, the ability to place all attached ports into promiscuous mode has been retained for diagnostics purposes.

Table 3-21. Special Network Options

Special Network Options

Offst

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0x01

PM

 

RSV

RSV

RSV

 

 

RSV

DI4

DI3

DI2

DI1

 

 

 

RSV

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reserved field (RSV)

Any field marked Reserved must be set to zero, else an error will be returned. This informs drivers which expect to be setting something with one of these bits that the function has been moved.

Disable on Initialization (DI1 through DI4)

Setting this bit causes the associated port to be disabled upon initialization, and requires that an Enable Port command be issued via the MAC Control IOPB to activate the port. This allows the host to initialize the controller, then set up various operational parameters for the individual ports, and then to enable the MAC port.

Promiscuous mode (PM)

Setting this bit will cause all attached ports to be placed in promiscuous mode.

Ethernet Physical Node Addresses

These four fields may contain a MAC address which will be used as the station address for the particular Ethernet port. If the contents of the field are zero, the station address stored in NVRAM will be used. Addresses specified here will not be saved in NVRAM.

Interrupt Levels and Vectors

The controller normal and controller error interrupt levels and vectors are used to report controller errors and status changes back to the host. This allows drivers to establish an independent entry point to handle exceptions, without affecting high-performance processing of network traffic.

DMA Burst Count

This field allows the host to control, to some extent, the characteristics of controller DMA transfers. Originally, the contents of this field determined the number of DMA transfers the controller would make in a single burst before releasing the bus and re-requesting it. The current bus controller uses a different mechanism, so values have been chosen that approximate that behavior, allowing substantial driver compatibility.

Using 0 (zero) in this field specifies "hog mode", where the controller after being granted the bus, the controller will transfer data until there is no data left.

75