Freescale Semiconductor MPC8260 - Manual (Page 1066)

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 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.
— The UUI field is stored for the host into the RxBD after 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.