Motorola PowerQUICC II MPC8280 Series Reference Manual page 1172

Features
— For each switched queue, a counter for the total number of packets in the queue
is available.
• CPS Receiver
— Segmentation of CPS PDU directly to external memory queues
— A separate queue for every VP | VC | CID or a common queue for multiple
VP | VC | CID combinations
— Receive one or multiple VP | VC | CIDs directly to a specific TX queue to enable
switching
— Sequence number (SN) protection check for CPS-PDU
— CRC5 (HEC) check to detect errors in the CPS-PH of the CPS-Packet
— OSF (offset field) of the STF (start of frame) check (a valid value is less than 48)
— An SDU length limit parameter (Max_SDU_Deliver_Length) per ATM VC
— Odd parity check for the STF octet of the CPS-PDU
• CPS Transmitter
— Reassemble CPS PDU directly from external memory
— Perform CPS-PDU padding as needed
— Insert Sequence Number bit of the CPS-PDU
— Parity bit is calculated to provide odd parity over the STF octet
— Calculation of CRC-5 on the first 19 bits of the CPS-PH
— UUI field in the CPS-Packet header is programmed according to the value of the
CPS_UUI parameter (per packet)
— A free running counter (per TX Queue) is decremented for each packet sent.
• SSSAR Receiver
— Reassemble CPS packets from the same CID into an SSSAR SDU
— A separate queue for every PHY | VP | VC | CID
— Perform all the above mentioned CPS receiver functions
— A Ras_Timer mode is provided. When the Ras_Timer expires the buffer is closed
with a timer expired error. The next packet received starts a new SSSAR SDU in
a new buffer.
— The SDU length is checked. If the frame exceeds the length limit
(SSSAR_Max_SDU_Length), the receiver discards the rest of the packets from
the current frame, closes the buffer and reports a Max_SDU violation error in the
BD. The next packet received starts a new SSSAR SDU in a new buffer.
— Partial Packet Discard. If no buffer is available when a packet arrives, the
receiver enters a frame hunt state and discards each incoming packet from the
current frame.
33-4
Freescale Semiconductor, Inc.
MPC8280 PowerQUICC II Family Reference Manual
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