IP178C-DS-R07 datasheet(42/93 Pages) ETC2

42 / 93 page

IP178C/IP178C LF/IP178CH/IP178CH LF

Datasheet

2.9

CoS

IP178C/IP178CH supports two type of CoS. One is port base priority function and the other is frame

base priority function. IP178C/IP178CH supports two levels of priority queues. A high priority packet will

be queued to the high priority queue to share more bandwidth. The ratio of bandwidth of high priority and

low priority queue is defined in MII register 30.1[15] or EEPROM 3[7].

2.9.1

Port base priority

The packets received from high priority port will be handled as high priority frames if the port base priority

is enabled. It is enabled by programming the corresponding bit in MII register 31.0[9]~31.8[9] or

EEPROM register 65[1] ~81[1]. Each port of IP178C/IP178CH can be configured as a high priority port

individually.

2.9.2

Frame base priority

VLAN tag and TCP/IP TOS

IP178C/IP178CH examines the specific bits of VLAN tag and TCP/IP TOS for priority frames if the frame

base priority is enabled. The packets will be handled as high priority frames if the tag value meets the

high priority requirement, that is, VLAN tag bigger than 3 or TCP/IP TOS field not equal to 3’b000. It is

enabled by programming the corresponding bit in MII register 31.0[10]~31.8[10] or EEPROM register

65[2]~81[2]. The frame base priority function of each port can be enabled individually.

IP178C/IP178CH supports an easy way to enable a sub set of CoS function without programming

EEPROM or MII registers. Port 6 and port 7 can be set as high priority ports if pin 100 P6_7_HIGH is

pulled high. Frame base priority function of all ports is enabled if pin 99 COS_EN is pulled high. The

setting in register takes precedence of the setting on pins.

byte

TYPE = 8100

VLAN field

TCI (tag control information)

12~13

14~15

TCI definition:

Bit[15:13]: User Priority 7~0

Bit 12: Canonical Format Indicator (CFI)

Bit[11~0]: VLAN ID.

IP178C uses bit[15:13] to define priority.

byte

TYPE = 0800

TOS field

IP HEADER

12~13

14~15

IP header definition:

Byte 14

Bit[7:0]: IP protocol version number & header length.

Byte 15: Service type

Bit[7~5]: IP Priority (Precedence ) from 7~0

Bit[1:0]: Reserved

IP178C uses bit[4:2] to define priority.

Bit 4: No Delay (D)

Bit 3: High Throughput

Bit 2: High Reliability (R)

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June 21, 2007

IP178Cx-DS-R12

IP178C-DS-R07 数据表(PDF) 42 Page - List of Unclassifed Manufacturers

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