Motorola MPC8260 - Manual (Page 832)

29-52 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA
Part IV. Communications Processor Module
Table 29-21. TCT Field Descriptions
Offset Bits Name Description
0x00 0Р1 С Reserved, should be cleared.
2 GBL Global. Asserting GBL enables snooping of data buffers, BDs, interrupt queues and
free buffer pool.
3Ð4 BO Byte ordering. This Þeld is used for data buffers.
00 Reserved
01 Power PC little endian
1x Big endian
5 Ñ Reserved, should be cleared.
6 DTB Data buffer bus
0 Reside on the 60x bus.
1 Reside on the local bus.
7 BIB BD, interrupt queue and external SRTS logic bus
0 Reside on the 60xbus.
1 Reside on the local bus.
Note: When using AAL5, AAL1 in UDC mode, BDs and data should be placed on the
same bus (TCT[DTB]=TCT[BIB]).
8 AVCF Auto VC off. Determines APC behavior when the last buffer associated with this VC
has been sent and no more buffers are in the VCÕs TxBD table,
0 The APC does not remove this VC from the schedule table and continues to
schedule it to transmit.
1 The APC removes this VC from the schedule table. To continue transmission after
the host adds buffers for transmission, a new ATM TRANSMIT command is needed,
which can be issued only after the CP clears the VCON bit. (Bit 13)
9 Ñ Reserved, should be cleared.
10Ð11 ATT ATM trafÞc type
00 Peak cell-rate pacing. The host must initialize PCR and the PCR fraction. Other
trafÞc parameters are not used.
01 Peak and sustain cell rate pacing (VBR trafÞc). The APC performs a continuous-
state leaky bucket algorithm (GCRA) to pace the channel-sustain cell rate. The host
must initialize PCR, PCR fraction, SCR, SCR fraction, and BT (burst tolerance).
10 Peak and minimum cell rate pacing (UBR+ trafÞc). The host must initialize PCR,
PCR fraction, MCR, MCR fraction, and MDA.
11 Reserved
12 CPUU CPCS-UU+CPI insertion (used for AAL5 only).
0 CPCS-UU+CPI insertion disabled. The transmitter clears the CPCS-UU+CPI Þelds.
1 CPCS-UU+CPI insertion enabled. The transmitter reads the CPCS-UU+CPI (16-bit
entry) from external memory. It should be placed after the end of the last buffer (it
should not be included in the buffer length).
13 VCON Virtual channel is on
Should be set by the host before it issues an
ATM TRANSMIT command. When the host
sets TCT[STPS] (stop transmit), the CP deactivates this channel and clears VCON
when the channel is next encountered in the APC scheduling table. The host can issue
another
ATM TRANSMIT command only after the CP clears VCON.
14Ð15 INTQ Points to one of four interrupt queues available.