cn8236 Mindspeed Technologies, cn8236 Datasheet - Page 94

• Manufacturer Part Number: cn8236
• Description: Atm Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

4.0 Segmentation Coprocessor
4.3 Segmentation Control and Data Structures
4-16
Table 4-6. Segmentation VCC Table Entry—AAL3/4, 5, and 0 Field Descriptions (2 of 2)
RUN
NX_EOM
CURR_PNTR
SCH
BCK_PM
VPC
SCH_GFR/
CBR_W_TUN
FLOW_ST
GFR_PRI
SCH_MODE
PRI
SCH_OPT
NEXT_VCC
SCH_STATE
Field Name
Flag that indicates segmentation is proceeding. This flag is set to one by the SAR when the host supplies
data for the VCC; it is set to zero by the SAR when the data available for the VCC is not sufficient to send
an entire ATM cell.
Indicates that the next cell is the end of a CPCS-PDU.
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 cell sent.
On a VCC with SCH_MODE = ABR this indicates a VP (instead of a VCC) connection, and RM cells are
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 4.1)
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
6.0.)
= Reserved
Mindspeed Technologies
Chapter
6.0, for details.)
Description
ATM ServiceSAR Plus with xBR Traffic Management
™
28236-DSH-001-B
CN8236