PM7367 datasheet(53/323 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

Field

Description

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 four and less than or equal to 32764.

The Receive Buffer Size field is valid in all RPDs.

The Receive Buffer Size and Data Buffer Start Address fields are written only by

the host. The RMAC reads these fields to determine where to store packet data.

All other fields are written only by the RMAC.

Receive Packet Descriptor Table

The Receive Packet Descriptor Table resides in host memory and stores all the

RPDs. The RPD Table can contain a maximum of 16384 RPDs. The base of

the RPD table is user programmable using the Rx Packet Descriptor Table Base

(RPDTB) register. The table is indexed by a Receive Packet Descriptor

Reference (RPDR) which is a 14-bit pointer defining the offset of a RPD from the

table base. Thus, as shown in the following diagram, a RPD can be located by

adding the RPDR to the Rx Packet Descriptor Table Base register.

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