MPC8280 datasheet(1016/1386 Pages) FREESCALE

1016 / 1386 page

ATM Controller and AAL0, AAL1, and AAL5

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

31-56

Freescale Semiconductor

31.10.2.3.6

VBR Protocol-Specific TCTE

Figure 31-34 shows the VBR protocol-specific TCTE.

Table 31-25 describes VBR protocol-specific TCTE fields.

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

—

Offset + 0x0E-1E

—

Figure 31-34. Transmit Connection Table Extension (TCTE)—VBR Protocol-Specific

Table 31-25. VBR-Specific TCTE Field Descriptions

Offset

Bits

Name

Description

0x00

—

SCR

Sustain cell rate. Holds the sustain cell rate (in slots) permitted for this channel according

to the traffic contract. To pace the channel’s sustain cell rate, the APC performs a

continuous-state leaky bucket algorithm (GCRA).

0x02

—

Burst tolerance. Holds the burst tolerance permitted for this channel according to the traffic

contract. The relationship between the BT and the maximum burst size (MBS) is

BT=(MBS-2)

× (SCR-PCR) + SCR.

0x04

—

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.

0x06

0–7

SRR

Sustain rate remainder. Holds the sustain rate remainder after adding the pace fraction

field to the additive channel sustain rate. Used by the APC to calculate the channel GCRA

(leaky bucket) state. Initialized to 0.

8–15

SCRF

Holds the sustain cell rate fraction of this channel in units of 1/256 slot.

0x08

—

Sustain rate. Used by the APC to hold the sustain rate after adding the pace field to the

additive channel sustain rate. Used by the APC to calculate the channel GCRA (leaky

bucket) state.

0x0C

VBR2

VBR type

0 Regular VBR. CLP=0+1 cells are rescheduled by PCR or SCR according to the GCRA

state.

1 VBR Type 2. CLP=0 cells are rescheduled by PCR or SCR according to the GCRA state.

CLP=1 cells are rescheduled by PCR.

1–15

—

Reserved, should be cleared.

0x0E–

0x1E

—

Reserved, should be cleared.

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