Interphase Tech CONDOR 4221 - Manual (Page 100)

Chapter 3 - MACSI Host Interface
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Command Options
Table 3-30. Command Options
Interrupt enable (IE)
As defined in Common IOPB Structures.
In-line gather (IG)
Setting this bit allows the host to define the frame location in system memory as a set of address/count pairs.
These gather elements are specified directly in the remainder of the IOPB, and do not require a separate DMA
of a gather-list.
Port selector
This field specifies the port to which the frame will be transmitted. Valid ports range from 0 to 3.
Disable multiple completion (DMC)
Setting this bit prevents the frame from being returned using the multiple completion mechanism.
Reserved bit (RSV)
Any bit marked Reserved must be set to zero. Failure to do so will cause an error to be returned to the host.
Transmit -- In-Line Gathers
By setting the IG bit in the Command Options field, the driver may define the data space for the frame to be transmitted
as a set of address/count pairs, or a gather list. By incorporating this directly in the Transmit IOPB, the controller saves
a separate DMA transfer of the gather list before beginning the DMA of the frame itself.
The gather list begins with the element immediately after the DMA Transfer Control Word (which controls the transfer
of each of the elements), and can continue for up to 8 elements. Note that if more than 2 elements are included, that
the resulting size of the IOPB exceeds normal, and the IOPB length field in the CQE must be set in order for the
controller to correctly process the command. This also means that fewer Command Queue Entries can be located in
short I/O if onboard IOPBs are employed.
Also note that the fields have been set up for long-word alignment to the structure elements, at the expense of
supporting fewer onboard CQE/IOPB’s. This is to accommodate RISC-based systems which make non-longword
aligned accesses difficult and expensive.
Command Options
Offst 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0x01 RSV DMC Port IG RSV RSV IE