RELEASED
PM7380 FREEDM-32P672
DATA SHEET
PMC-1990262
ISSUE 5
FRAME ENGINE AND DATA LINK MANAGER 32P672
Field
CE
Description
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 RMAC672
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 RMAC672 from the
Receive Free Queues, each of which is assumed to point
to only one buffer, i.e. not a chain.
Offset[1:0]
Status [5:0]
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.
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 .
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA,INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
48
PMC [ PMC-SIERRA, INC ]
