Motorola MPC8260 - Manual (Page 836)

29-56 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA
Part IV. Communications Processor Module
Table 29-24 describes AAL0 protocol-speciÞc TCT Þelds.
29.10.2.3.4 VBR Protocol-SpeciÞc TCTE
Figure 29-34 shows the VBR protocol-speciÞc TCTE.
Table 29-25 describes VBR protocol-speciÞc TCTE Þelds.
Table 29-24. AAL0-Specific TCT Field Descriptions
Offset Bits Name Description
0x10 0Р7 С Reserved, should be cleared.
8 0 Must be 0.
9 CR10 CRC-10
0 CRC10 insertion is disabled.
1 CRC10 insertion is enabled.
10 Ñ Reserved, should be cleared.
11 ACHC ATM cell header change
0 Normal operation ATM cell header is taken from AAL0 buffer.
1 VPI/VCI (28 bits) are taken from TCT.
12Р15 С Reserved, should be cleared.
0x12Ð
0x14 С С Reserved, should be cleared.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Offset + 0x00 SCR
Offset + 0x02 Burst Tolerance (BT)
Offset + 0x04 Out of Buffer Rate (OOBR)
Offset + 0x06 Sustain Rate Remainder (SRR) SCR Fraction (SCRF)
Offset + 0x08 Sustain Rate (SR)
Offset + 0x0A
Offset + 0x0C VBR2 Ñ
Offset + 0x0E-1E Ñ
Figure 29-34. Transmit Connection Table Extension (TCTE)ÑVBR Protocol-
Specific
Table 29-25. VBR-Specific TCTE Field Descriptions
Offset Bits Name Description
0x00 Ñ SCR Sustain cell rate. Holds the sustain cell rate (in slots) permitted for this channel according to
the trafÞc contract. To pace the channelÕs sustain cell rate, the APC performs a continuous-
state leaky bucket algorithm (GCRA).
0x02 Ñ BT Burst tolerance. Holds the burst tolerance permitted for this channel according to the trafÞc
contract. The relationship between the BT and the maximum burst size (MBS) is BT=(MBS-2)
´ (SCR-PCR) + SCR.
0x04 Ñ OOBR Out-of-buffer rate. In out of buffer state (when the transmitter tries to open TxBD whose R bit
is not set) the APC reschedules the current channel according to OOBR rate.