PM7367 datasheet(73/323 Pages) PMC

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PM7367 FREEDM-32P32

DATA SHEET

PMC-1991499

ISSUE 2

FRAME ENGINE AND DATA LINK MANAGER

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

enabled, free TDRs are written into the TDRF queue six at a time, to reduce the

number of host memory accesses. The Free Queue cache is also flushed to the

TDRF queue if the Interrupt On Completion (IOC) bit is set in the TD, which

sends the corresponding TDR directly to the TDRF queue.

The queues, shown in Figure 12 are defined by a common base pointer residing

in the Transmit Queue Base register and eight offset pointers, four per queue.

For each queue, two pointers define the start and the end of the queue, and two

pointers keep track of the current read and write locations within the queue. The

read pointer for each queue points to the offset of the last valid TDR read, and

the write pointer points to the offset where next TDR can be written. The end of

a queue is not a valid location for a TDR to be read or written. A queue is empty

when the read pointer is one less than the write pointer or if the read pointer is

one less than the end pointer and the write pointer equals the start pointer. A

queue is full when the read pointer is equal to the write pointer. Each queue

element is 32 bits in size, but only the 17 least significant bits are valid. The 17

least significant bits consist of a 14-bit TDR and three status bits. The status bits

are used by the TMAC to inform the host of the success or failure of

transmission (see Table 10). When the TMAC writes TDRs to the TDRF queue,

it sets bits [23:17] of the queue element to 0. Once a TDR is placed on the

TDRF queue, the FREEDM-32P32 will make no further accesses to the TD nor

the associated buffer.

Note that the maximum value to which an end pointer may be set is FFFF hex,

resulting in a maximum offset from the queue base address of (4*(FFFF-1)) =

3FFF8 hex. An end pointer must not be set to 0 hex in an attempt to include

offset 3FFFC hex in a queue.

PM7367 数据表(PDF) 73 Page - PMC-Sierra, Inc