PM7366-PI datasheet(53/286 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

Offset[1:0]

The Offset[1:0] bits indicate the byte offset of the data packet from the

start of the buffer. If this value is non-zero, there will be ‘dummy’ (i.e.

undefined) bytes at the start of the data buffer prior to the packet data

proper.

For a linked list of RPDs, only the first RPD's Offset field is valid. All

other RPD Offset fields of the linked list are set to 0.

Status [5:0]

The Status[5:0] bits indicate the status of the received packet.

Status[0]

Rx buffer overrun

Status[1]

Packet exceeds max. allowed size

Status[2]

CRC error

Status[3]

Packet Length not an exact no. of bytes

Status[4]

HDLC abort detected

Status[5]

Unused (set to 0)

For a linked list of RPDs, only the last RPD's Status field is valid. All

other RPD Status fields of the linked list are invalid and should be

ignored. When a packet requires only one RPD, the Status field is

valid.

Bytes in Buffer [15:0]

The Bytes in Buffer[15:0] bits indicate the number of bytes actually

used in the current RPD's data buffer to store packet data. The count

excludes the 'dummy' bytes inserted as a result of a non-zero Offset

field. A count greater than 32767 bytes indicates a packet that is

shorter than the expected length of the FCS field.

The Bytes in Buffer field is invalid when Status[0] or Status[4] is

asserted .

Next RPD Pointer

[13:0]

The Next RPD Pointer[13:0] bits store a RPDR which enables the

RMAC to support linked lists of RPDs. This field, which is only valid

when CE is equal to logic zero, contains the RPDR to the next RPD in

a linked list. The RMAC links RPDs when more than one buffer is

needed to store a packet.

The Next RPD Pointer is not valid for the last RPD in a linked list

(when CE=1). When a packet requires only one RPD, the Next RPD

Pointer field is not valid.

Receive Buffer Size

[15:0]

The Receive Buffer Size[15:0] bits indicate the size in bytes of the

current RPD's data buffer. This field is expected to be configured by

the Host during initialisation. The Receive Buffer Size must be a non-

zero integer multiple of 16 and less than or equal to 32752.

The Receive Buffer Size field is valid in all RPDs.

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