PM7364 datasheet(79/325 Pages) PMC

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PM7364 FREEDM-32

DATA SHEET

PMC-1960758

ISSUE 6

FRAME ENGINE AND DATA LINK MANAGER

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

Field

Description

Host TD Pointer [13:0] A copy of the Host Next TD Pointer field of the TD

currently being read, i.e. a pointer to the next TD in the

chain currently being read. (See Figure 14)

DMA Current

Address[31:0]

The DMA Current Address [31:0] bits hold the address

of the next dword in the current buffer. This field is

incremented on each access to the buffer.

Indicates if the linked list of packets for this channel

contains more than one host-linked chain (See Figure

14). If the V bit is set to logic 1, the list contains more

than one chain and the next and last TD pointer fields

are valid. If the V bit is set to logic 0, the list is either

empty or contains only one host-linked chain and the

next and last TD pointer fields are invalid.

Next TD Pointer [13:0] Offset to the head of the next host-linked chain of TDs

to be read. (See Figure 14)

Transmit Descriptor Linking

As described above, the TCDR table contains pointers which the TMAC uses to

construct linked lists of data packets to be transmitted. After the host places a

new TDR in the TDR Ready queue, the TMAC retrieves the TDR and links it to

the TD pointed at by the Last TD Pointer field. The TMAC may create up to 256

linked lists, viz. a high-priority list and a low-priority list for each DMA channel.

Whenever a new data packet is requested by the downstream block, the TMAC

picks a packet from the high-priority linked list unless it is empty, in which case, a

packet from the low-priority linked list is used.

PM7364 Datasheet(PDF) 79 Page - PMC-Sierra, Inc