PM7366-PI datasheet(52/286 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

Receive Packet Descriptor

The Receive Packet Descriptors (RPDs) pass buffer and packet information between the RMAC

and the host. Both the RMAC and the host read and write information in the RPDs. The host

writes RPD fields which describe the size and address of data buffers in host memory. The

RMAC writes RPD fields which provide number of bytes used in each data buffer, RPD link

information, and the status of the received packet. RPDs are stored in host memory in a Receive

Packet Descriptor Table which is described in a later section. The Receive Packet Descriptor

structure is shown in Figure 4.

Figure 4 – Receive Packet Descriptor

Reserved (18)

Next RPD Pointer [13:0]

Status [5:0]

RCC [6:0]

Data Buffer Start Address [31:0]

Receive Buffer Size [15:0]

Bit 31

Bytes In Buffer [15:0]

Reserved (16)

Offset[1:0]

Table 8 – Receive Packet Descriptor Fields

Field

Description

Data Buffer Start

Address[31:0]

The Data Buffer Start Address[31:0] bits point to the data buffer in host

memory. This field is expected to be configured by the Host during

initialisation.

The Data Buffer Start Address field is valid in all RPDs.

RCC[6:0]

The Receive Channel Code (RCC[6:0]) bits are used by the RMAC to

indicate which channel an RPD is associated with.

For a linked list of RPDs, all the RPDs’ RCC fields are valid, i.e. all

contain the same channel value.

The Chain End (CE) bit indicates the end of a linked list of RPDs.

When CE is set to logic one, the current RPD is the last RPD of a

linked list of RPDs. When CE is set to logic zero, the current RPD is

not the last RPD of a linked list.

The CE bit is valid for all RPDs written by the RMAC to the Receive

Ready Queue. When a packet requires only one RPD, the CE bit is

set to logic one. The CE bit is ignored for all RPDs read by the RMAC

from the Receive Free Queues, each of which is assumed to point to

only one buffer, i.e. not a chain.

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