AAL2 Implementation
MPC885 PowerQUICC Family Reference Manual, Rev. 2
44-16
Freescale Semiconductor
44.5.2
AAL2_Rx_Queue
Similar to an RxBD table, a channel’s AAL2_Rx_Queue consists of a circular table of RPDs.
AAL2_Rx_Queue parameters are defined in each channel’s AAL2_RCT. The queue pointer
(AAL2_RQ_PTR) is advanced by AAL2.
Figure 44-7
shows an example AAL2_Rx_Queue with six RPDs. The second and third RPDs (shaded)
have been filled (E=0). Because the INT bits are set in the third and sixth RPDs, AAL2 will generate
interrupts to the host after the CPS-Packets associated with these RPDs have been retrieved.
Figure 44-7. AAL2_Rx_Queue Example
0x02
13
E7
Indicates whether a HEC error occurred in the CPS-Packet header of a packet overlapping
a CPS-PDU boundary.
0 No HEC error occurred for the overlapping packet.
1 A HEC error occurred for the overlapping packet; if the value of the OSF is less than 47,
processing starts at the octet pointed to by the OSF. When this error is indicated, the
CPS-Packet associated with this RPD is not valid. Host should clear this bit after
processing the RPD.
Host should clear this bit during initialization.
0x02
14–15
—
Reserved, should be cleared.
0x04
—
RP_PTR
Pointer to the receive CPS-Packet. RP_PTR points to the beginning of the CPS-Packet
which resides in external memory.
This pointer is specified by the host, and must be burst aligned (RP_PTR[28–31]=0). AAL2
does not modify this field
Table 44-4. RPD Field Descriptions (continued)
Offset
Bits
Name
Description
AAL2_RQ_BASE
AAL2_RQ_PTR
E=1 W=1 INT=1
E=0 W=0 INT=0
E=0 W=0 INT=1
E=1 W=0 INT=0
E=1 W=0 INT=0
E=1 W=0 INT=0
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