The Transmit Parameter List is shown in Figure 3-19.
FORWARD POINTER FORWARD POINTER TRANSMIT CSTAT
FRAME SIZE 1 *
I
DATA COUNTDATA ADDRESS (high) DAT A ADDRESS (low) 1 *
I
DATA COUNTDAT A ADDRESS (high) DAT A ADDRESS (low) 0*
I
DATA COUNTDAT A ADDRESS (high) DAT A ADDRESS (low)
*BIT ZERO VALUE.
Figure 3-19. TRANSMIT Parameter List shown with three Data Counts
3-50 Token-Ring Network Adapter
Table 3-15 describes each of the fields in the TRANSMIT Parameter List.
Table 3-15. TRANSMIT Parameter List Fields FORWARD POINTER
FRAME SIZE
This 32-bit field contains a 24-bit address which is a pointer to the next Transmit Parameter List in the chain. When this address is ODD, it denotes that the current Transmit List is the last in the chain. The Adapter will continue to process Transmit Lists until it reads an ODD address. It will then wait for the last frame (list with ODD address) to be transmitted onto the ring. If the system updates the
FOR WARD POINTER before the last frame is transmitted, the Adapter will continue to process the Transmit Lists. If not, the TRANSMIT command will complete and another must be issued to continue. The system must update the FORWARD POINTER from the most significant byte to the least significant byte to ensure that the address is valid before changing to an EVEN address. Frames, not lists that define partial frames, should be added to the chain. The FOR WARD POINTER should not be initialized to point to itself, as problems may occur due to the pipelined nature of list processing employed by the Adapter. Transmit Lists must be aligned on even byte boundaries. The Adapter will not alter this parameter.
This 16-bit field contains the number of bytes to be transmitted as a frame. The FRAME SIZE value includes AC/ FC, DESTINATION and SOURCE ADDRESS, the Routing Field, and the Information Field. FRAME SIZE does not include CRC, FS, or ED. This parameter is valid only for the Transmit List that has the FRAME START bit set. FRAME SIZE must be in all lists. The Adapter will not alter this parameter. A frame size of zero is not valid. The maximum frame size which can be transmitted may be calculated as (BUFFER SIZE -8) x TRANSMIT BUFFER MAXIMUM COUNT.
Table 3-15. TRANSMIT Parameter List Fields (Continued) DATA COUNT
DATA ADDRESS
TRANSMIT CST A T
3-52 Token-Ring Network Adapter
This 16-bit field contains the number of bytes to be
transmitted starting from the address defined in the DATA ADDRESS parameter. There can be a maximum of three DATA COUNT/DATA ADDRESS parameters to provide a gather write capability per Transmit List (not frame). If Bit 0 is zero, it is the last DATA COUNT in the Transmit List. Bit
o
of the third DATA COUNT is ignored. A DATA COUNT of 0 is permitted (with or without Bit 0 set). The sum of the used DATA COUNT parameters must equal the FRAME SIZE specified on the Start of Frame List. The DATA COUNT can be even or odd. The Adapter will not alter this parameter.This 32-bit field contains the 24-bit address of the data to be transmitted. DATA ADDRESS may be even or odd. The Adapter will not alter this parameter.
TRANSMIT COMMAND/STATUS. This 16-bit parameter is set by the attached system when the Transmit List is created. It is over-written by the Adapter to report frame completion status. When initially set by the attached system, this parameter field is referred to as the TRANSMIT CST A T REQUEST field. After a frame completes
transmission, the Adapter will overwrite bits in this field only in the list which starts the frame. These bits indicate the completion status of the frame. This parameter field is referred to as the TRANSMIT CSTAT COMPLETE. Note that command and status information within the
TRANS MIT CST AT field is associated with frames and not the TRANSMIT command directly.
TRANSMIT CSTAT REQUEST.
The CST AT bits are set by the attached system as follows:
BIT 0 VALID. The Adapter will wait for bit 0 to be set to a one before processing the current Transmit List. The attached system must issue a TRANSMIT VALID Interrupt Request when changing VALID bits from a zero to a one. This bit is ignored unless the list is an anticipated start of frame (i.e.
follows End of Frame or is first list of command).
Table 3-15. TRANSMIT Parameter List Fields (Continued)
FRAME COMPLETE. Bit I should be reset to zero.
FRAME INTERRUPT. Setting bit 4 to one will cause the Adapter to interrupt when the frame has been transmitted, rather than waiting for all frames on the chain to be transmitted. This bit is ignored unless START OF FRAME (bit 2) is a one.
RESERVED. Bits 5-15 should be set to zero.
TRANSMIT CST AT COMPLETE. This 16-bit field is loaded, on a list which starts a frame only, with the completion code for the transmitted frame (not TRANSMIT command) when the Adapter has transmitted a frame. CSTATs which are not in a list which defines the start of a frame, are not altered by the Adapter. The TRANSMIT CST AT COMPLETE bit definitions are shown below:
BITO the frame transmit or strip process was in error.
Table 3-15. TRANSMIT Parameter List Fields (Continued) BITS 6-7 BIT 8-15