PM7366-PI datasheet(70/286 Pages) PMC

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PM7366 FREEDM-8

DATA SHEET

PMC-1970930

ISSUE 4

FRAME ENGINE AND DATA LINK MANAGER

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA,INC., AND FOR ITS CUSTOMERS’ INTERNAL USE

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.

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