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Transmit List Format
5-12
Table 5–4. Transmit Parameter List Fields
Field Definition
Forward pointer This 32-bit field contains a pointer to the next transmit parameter list in the chain. The
three LSBs of this field are ignored, as lists must always be on an eight-byte address
boundary. When the forward pointer is 0, the current transmit parameter list is the last
in the chain. The adapter processes transmit parameter lists until it reads a list with a
0 forward pointer. Once the frame pointed to by this list has been read into the adapter
and the transmit CSTAT complete field written, the transmit channel stops. A Tx EOC
interrupt is raised for the channel, but this is not seen by the host (because of interrupt
prioritization) until all outstanding Tx EOF interrupts have been acknowledged.
The system must update the forward pointer as a single 32-bit write operation to ensure
the adapter does not read the field while it is being updated. The forward pointer is read
at the same time as the rest of the list structure. The adapter does not alter this field.
Frame size This 16-bit field contains the total number of bytes in the transmit frame. This field must
be equal to the sum of the data count fields, or an adapter check occurs.
Transmit CSTAT This 16-bit parameter is written by the host when the transmit parameter list is created.
It is overwritten by the adapter to report frame transfer status. When initially written by
the host, this field is referred to as the transmit CSTAT request field.
After a frame is transferred into the adapter, the adapter overwrites this field and it is re-
ferred to as the transmit CSTAT complete field. This indicates completion of frame trans-
fer into the adapter FIFO, not frame transmission or completion of the transmit com-
mand.
The bit definitions for these two fields are defined in later tables.
Data count This 32-bit field indicates the number of frame data bytes to be found at the address indi-
cated by the following data address field. There can be a maximum of ten data count/
data address parameters in a list.
If bit 31 is set to a 1, then this is the last data count in the list. A data count of 0 is only
permitted when it follows the last fragment in multifragment mode. This is only necessary
when nine or less fragments are used.
Data address
This 32-bit field contains a pointer to a fragment (or all) of the frame data in host (PCI)
address space. Data address is a byte address. Frame fragments can start and end on
any byte boundary.