ATM Controller
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
39-17
39.4.2
PTP Switching and PM
Performance monitoring (PM) is not available when routing multiple RCTs to one TCT. However, PM is
allowed for dedicated PTP RCT/TCT pairs.
39.4.3
PTP Buffers
PTP buffers follow the AAL0 buffer structure. See
Section 37.1.2, “AAL0 Buffers.”
39.4.4
PTP Buffer Descriptors
The PTP BD, shown in
Figure 39-11
, is common to the receiver and transmitter. PTP BDs can be thought
of as modified TxBDs because they use the TxBD base pointers (TBDBASE in the parameter RAM and
PTP TCT[PTP_BD_PTR,PTP_BASE]). The same PTP BD format is used for both UTOPIA and serial
ATM.
Table 39-5
describes the PTP BD fields.
1
0
1
Reserved
1
1
1
Reserved
0
1
2
3
4
15
0
V
-
W
I
—
2
—
4
PTP Buffer Pointer
8
—
A
—
Figure 39-11. PTP Buffer Descriptor
Table 39-5. PTP BD Field Descriptions
Offset from
PTP_BD_PTR
Bits
Name
Description
0x00
0
V
Valid (ready for switching). Should be cleared during initialization.
0 Empty. The data buffer associated with this BD is not ready for switching
(transmission). The receiver is free to manipulate this BD and its associated
data buffer. The receiver sets this bit after the cell has been received.
1 Ready. The data buffer has been prepared for switching (received) but has not
been sent or is currently being sent. The transmitter clears this bit after cell
transmission.
1
—
Reserved
Table 39-4. Available PTP Options (continued)
IAQ
ITQ
AVCO
TX Action
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