PM7366-PI datasheet(72/286 Pages) PMC

72 / 286 page

RELEASED

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

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 12). 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-8 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.

PM7366-PI датащи(PDF) 72 Page - PMC-Sierra, Inc