ATM AAL2
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
32-4 Freescale Semiconductor
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 th e 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.
The UUI field is stored for the host into the RxBD aft er receiving the whole SSSAR frame.
SSSAR Transmitter
Segmentation of SSSAR SDUs from SSSAR TX queue into CPS packets
An SSSAR TX queue may contain several CIDs
Performs all the above mentioned CPS transmitter functions
A programmable segment length (Seg_Len) is copied from the SSSAR SDU into the CPS
packet payload, except for when at the end of the frame or buffer.
UUI mode available. When UUI mode is enabled, the SSSAR UUI is copied from the byte
following the last byte of the frame.