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RELEASED
DATA SHEET
PM7366 FREEDM-8
ISSUE 4
PMC-1970930
FRAME ENGINE AND DATA LINK MANAGER
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA,INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
57
Field
Description
TMAC Next TD Pointer
[13:0]
The TMAC Next TD Pointer[13:0] bits are used to store TDRs
which permits the TMAC to create linked lists of TDs passed to it
via the TDRR queue. The TDs are linked with other TDs
belonging to the same channel and same priority level. In the
case that data presented to the TMAC is returned to the host due
to a channel becoming unprovisioned, a TDR pointing to the start
of the per-channel linked list of TDs is placed on the TDRF
queue. It is the responsibility of the host to follow the TMAC and
host links in order to recover all the buffers.
ABT
The Abort (ABT) bit is used by the host to abort the transmission
of a packet. When ABT is set to logic 1, the packet will be
aborted after all the data in the buffer has been transmitted. If
ABT is set to logic 1 in the current TD, the M bit must be set low
and the CE bit must be set to high..
IOC
The Interrupt On Complete (IOC) bit is used by the host to
instruct the TMAC to interrupt the host when the current TD's
data buffer has been read. When IOC is logic 1, the TMAC
asserts the IOCI interrupt when the data buffer has been read.
Additionally, the Free Queue FIFO will be flushed. If IOC is logic
zero, the TMAC will not generate an interrupt and the Free
Queue FIFO will operate normally.
Host Next TD Pointer [13:0]
The Host Next TD Pointer[13:0] bits are used to store TDRs
which permits the host to support linked lists of TDs. As
described above, linked lists of TDs are terminated by setting the
CE bit to logic 1. Linked lists of TDs are used by the host to pass
multiple TD packets or multiple packets associated with the
same channel and priority level to the TMAC.
Transmit Buffer Size [15:0]
The Transmit Buffer Size[15:0] field is used to indicate the size in
bytes of the current TD's data buffer. (N.B. The TMAC does not
make use of this field.)
Transmit Descriptor Table
The Transmit Descriptor Table, which resides in host memory, contains all of the Transmit
Descriptors referenced by the TMAC. To access a TD, the TMAC takes a TDR from a TDRR
queue or from the TCDR table and adds 16 times its value (because each TD is 16 bytes in size)
to the Transmit Descriptor Table Base (TDTB) pointer to form the actual address of the TD in host
memory. Each TD must reside in the Transmit Descriptor Table. The Transmit Descriptor Table
can contain a maximum of 16384 TDs. The base of the Transmit Descriptor Table is user
programmable using the TMAC Tx Descriptor Table Base register. Thus, as shown below, each
TD can be located using a Transmit Descriptor Reference (TDR) combined with the TMAC Tx
Descriptor Table Base register.