cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 93

• Manufacturer Part Number: cn8237
• Description: Atm Oc-12 Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

CN8237
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
28237-DSH-001-C
Table 4-3. Segmentation VCC Table Entry—AAL5 and 0 Field Descriptions (2 of 2)
CURR_PNTR
SCH
BLK_PM
VPC
SCH_GFR/
CBR_W_TUN
FLOW_ST
GFR_PRI
SCH_MODE
PRI
SCH_OPT
NEXT_VCC
SCH_STATE
Reserved
Field Name
Pointer to the current buffer descriptor for the VCC. This field is automatically updated by the SAR. The
two least significant bits of the pointer are assumed to be 0 (word-aligned). The address of the
descriptor is (CURR_PNTR << 2) or (CURR_PNTR x 4).
Indicates VCC is currently scheduled for segmentation.
Toggled after each backward reporting PM cell is scheduled. Used to prevent PM information in PM
table from being overwritten before the cell is sent.
On a VCC with SCH_MODE = ABR this indicates a VP (instead of a VCC) connection, and RM cells will
be generated on VCI = 6.
If SCH_MODE = GFR, this bit set to a logic high indicates that the VCC is currently scheduled on a
GFR_PRI priority queue for segmentation. The SCH bit set to a logic high indicates that the VCC is
currently scheduled on a VBR priority queue. This host does not have to set this bit—it is set by the SAR.
If SCH_MODE = CBR, this bit set to a logic high specifies that an unused CBR schedule slot should be
used as a tunnel slot, with tunnel priorities specified in word 7 of the VCC table entry.
Flow control state. This bit is active only in ER mode. Indicates that the priority of the connection is
increased to insure MCR.
Specifies the UBR priority level for a GFR service connection. GFR_PRI must be < PRI.
Traffic class of VCC. (See
000 UBR = Unspecified Bit Rate
001 CBR = Constant Bit Rate
010
011 GFR = Guaranteed Frame Rate
100 VBR1 = Single Leaky Bucket VBR
101 VBR2 = Dual Leaky Bucket VBR with both buckets always active
110 VBRC= Dual Leaky Bucket VBR with bucket 1 applied only to CLP = 0 cells
111 ABR = Available Bit Rate (as specified by TM 4.0)
Segmentation priority. The lowest priority is 0. The highest priority is 15. This field is not active when
SCH_MODE is CBR. When SCH_MODE is GFR, this specifies the VBR priority.
Schedule option. The use of this bit depends on the setting of the SCH_MODE field.
VBR1, VBR2, VBRC, ER: Initializes bucket state to send maximum burst. The SAR writes this bit to 0
after bucket state initialized.
CBR: Indicates that the next cell slot opportunity should be skipped. This bit is written by the host and
cleared by the SAR after the cell slot is skipped.
If this bit is changed while the VCC is active, only the byte containing the bit should be written.
Used by SAR to link VCCs in schedule chains.
Specific scheduling state information. The contents of this field depend on the setting of the SCH_MODE
field. It is not used when SCH_MODE is set to UBR. (The contents of this field are detailed in
Chapter
Always set to 0.
6.0.)
including setup values for restricted fields.
differs from the AAL5-AAL0 format.
= Reserved
Table 4-4
Mindspeed Technologies
shows the format for Virtual FIFO buffer VCC table entries,
Chapter 6.0
for details.)
Description
™
4.3 Segmentation Control and Data Structures
Table 4-5
4.0 Segmentation Coprocessor
describes the field that
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