Freescale Semiconductor MPC8260 - Manual (Page 1075)

ATM AAL2
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 32-13
32.3.5.2 CPS Tx Queue Descriptor
Each CPS TxBD table is managed by a CPS Tx queue descriptor (TxQD), as shown in Figure 32-7 . The
TxQD contains the address of the next BD to be serviced, and other queue-specific parameters. The
NextQueue pointer is used to create a linked list of TxQDs, as described in
Section 32.3.2, “Transmit
Priority Mechanism.” The CPS TxQD is located in the dual-port RAM, in a 16-byte aligned address.
0x1C 0–1 — Reserved, should be cleared during initialization.
2–7 PMT Performance monitoring table. Points to one of the available 64
performance monitoring tables. The starting address of the table is
PMT_BASE+PMT*32.
8–15 MaxStep Holds the number of TX Queues visited for each cell being prepared for
transmission. In fixed priority mode (TCT[Fix]=1), MaxStep should be set
to the total number of TX queues in the channel. See
Section 32.3.2,
“Transmit Priority Mechanism .”
0x1E 0-1 — Reserved, should be cleared during initialization.
2–7 PFT Partial fill threshold. Used for partially filled cells only; see Section 32.3.3,
“Partial Fill Mode (PFM) .” Specifies the maximum number of packet bytes
allowed in a CPS PDU. The range 1–48 are valid values.
If PFT=48 in partial fill mode, performance is adversely affected. When
not in partial fill mode, PFT must be initialized to 47.
8-11 — Reserved, should be cleared during initialization.
12 OneP One packet per queue. See Section 32.3.2, “Transmit Priority
Mechanism .”
0 The transmitter reads as many packets as possible from each TX queue
before moving to the next queue.
1 The transmitter reads only one packet from each TX queue before
advancing to the next queue.
13 STPT Stop transmit. Should be cleared during initialization. When the host sets
this bit, the CP removes this channel from the APC and clears
TCT[VCON] flag.
14 Fix Fixed priority. See Section 32.3.2, “Transmit Priority Mechanism .”
0 Round robin priority. The TX Queues related to this channel all share
the same priority.
1 Fixed priority. The TX Queues are ordered in a fixed priority ladder.
15 PM Performance monitoring
0 No performance monitoring for this VC.
1 Performance is monitored for this VC. When a cell is sent for this VC,
the performance monitoring table indicated in PMT field is updated.
1
Boldfaced entries must be initialized by the user.
Table 32-1. AAL2 Protocol-Specific Transmit Connection Table (TCT)
Field Descriptions (continued)
Offset Bits Name
1
Description