Motorola PowerQUICC II MPC8280 Series Reference Manual page 1191

Header
AAL2 RCT
CID mapping table base
CID mapping table
CID0
RxQD offset
CID1
RxQD offset
•
•
•
CID255
RxQD offset
RxQD offset
Half-word
RxQD_Base_Ext + 512*4
(in FCC parameter RAM)
33.4.3 AAL2 Switching
Switching is performed by pointing an RX CID at a switch RxQD (see Figure 33-14). The
switch RxQD is unique for each Rx CID. The descriptor holds a translation CID number
and a pointer to a CPS TxQD into which this packet is saved and later sent by the
transmitter. (The TxQD pointer is responsible for the actual PHY | VP | VC switching.) The
TxQD pointed to by the switch RxQD(s) should have TxQD[SW] set and should not be
modified by the host when the channel is active. The transmit scheduling of the packet is
done by the APC according to the programmed bit rate of the ATM channel that holds the
switched queue.
MOTOROLA
Freescale Semiconductor, Inc.
ATM cell
STF CID-PH CPS packet payload
RxQD_Base_Int
(in FCC parameter RAM)
RxQD_Base_Int +
RxQD_Offset*4
2044
2048
Figure 33-13. CID Mapping Process
Chapter 33. ATM AAL2
For More Information On This Product,
Go to: www.freescale.com
CID-PH CPS packet payload
RxQD table (internal)
0
Reserved
32
SSSAR RxQD
64
CPS RxQD
72
Switch RxQD
Tx queue descriptor
RxQD table (external)
CPS RxQD
Switch RxQD
AAL2 Receiver
RxBD table Rx buffers
RxBD table Rx buffers
Tx buffers
TxBD table
33-23