cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 82

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

4.0 Segmentation Coprocessor
4.2 Segmentation Functional Description
Figure 4-1. Segmentation VCC Table
4-2
4.2.1.1 Segmentation
(SEG_VBASE(SEG_VCCB)<<7)
VCC Table
Base Register
VCC_INDEX = 0xFFFD
VCC_INDEX = 0x1000
specific VCC table entry (seven words) and a service class specific Schedule
State (SCH_STATE). For non-ABR VCCs, the remaining three words of the
channel descriptor form the SCH_STATE entry. For an ABR VCC, the
SCH_STATE entry contains 13 words, which require an additional descriptor
location.
Figure 4-1
VCC located at VCC_INDEX 0x1000, and a non-ABR VCC at VCC_INDEX
0xFFFD. The host allocates the VCC table in SAR SEG-shared memory and
provides an address to the SAR in a base register field,
SEG_VBASE(SEG_VCCB). For the most efficient ABR performance, all ABR
VCCs should be placed in the upper half of the VCC table (that is, with smaller
VCC indexes). The only reason not to put ABR VCCs at the lowest address range
is to place CBR VCCs in the first 32 K of VCC addresses. Valid VCC indexes for
CBR traffic range from 0x0000 to 0x7FFE, due to the limit imposed by a 15-bit
address. A VCC index of 0xFFFF for non-CBR and 0x7FFF for CBR indicates a
NULL VCC.
indexes, the actual number of segmentation VCCs allowed by the SAR is limited
by the amount of SAR SEG-shared memory available in which to allocate and
create segmentation VCC tables, transmit queues, etc.
(non-ABR VCC)
VCC_INDEX = 0x3
A Segmentation VCC table channel descriptor consists of two parts: an AAL
While the CN8237 will accept any VCC index within the range of 64 K VCC
(ABR VCC)
(CBR VCC)
Mindspeed Technologies
shows a VCC table with a CBR VCC at VCC_INDEX 3, an ABR
VCC Table Entry
VCC Table Entry
VCC Table Entry
SCH_STATE
SCH_STATE
SCH_STATE
VCC Table
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
VCC_INDEX = 0x0
}
}
}
}
}
10 Words = 1 Descriptor
7 Words
7 Words
13 Words
3 Words
™
}
}
2 Descriptors
1 Descriptor
28237-DSH-001-C
CN8237
8237_028