AN983 datasheet(70/91 Pages) ETC

70 / 91 page

AN983B

PCI/miPCI Fast Ethernet Controller with integrated PHY

The PAUSE function operation is used to inhibit transmission of data frames for a specified period of

time. The AN983B supports full duplex protocol of IEEE802.3x. To support PAUSE function, the

AN983B

implements the MAC Control Sub-layer functions to decode the MAC Control frames

received from MAC control clients and execute the relative requests accordingly. When the Full

Duplex mode and PAUSE function are selected after Auto-Negotiation completed, then the AN983B

enables the PAUSE function for flow control of full duplex application. In this section we will

describe how the AN983B implements the PAUSE function.

MAC Control Frame and PAUSE Frame

Destination Address

Source Address

Length/Type=88-08h

MAC Control OPcode

MAC Control Parameter

Reserved(pads with zeroes)

6 Octets

2 Octets

(minFrameSize-160) / 8 Octets

Fig -

MAC Control Frame Format

The MAC Control frame is distinguished from other MAC frames only by their Length/Type

field identifier.

The MAC Control Opcode defined in MAC Control Frame format for PAUSE

function is 0001h.

Besides, the PAUSE time is specified in the MAC Control Parameters

field with 2 Octets, unsigned integer, in the units of Slot-Times.

The range of possible

PAUSE time is 0 to 65535 Slot-Times.

So, a valid PAUSE frame issued by a MAC control client (could be a switch or a bridge) will

contains:

1) The destination address is set equal to the globally assigned 48 bit mulitcast address

01-80-C2-00-00-01, or equal to the unicast address which the MAC control client wishes to

inhibit its transmission of data frames.

2) Filled the MAC Control Opcode field with 0001h.

3) 2 Octets of PAUSE time specified in the MAC Control parameter field to indicate the

length of time for which the destination is wished to inhibit data frame transmission.

Receive Operation for PAUSE function

Upon reception of a valid MAC Control frame, the AN983B will start a timer for the length of

time specified by the MAC Control Parameters field.

When the timer value reaches zero

then the AN983B ends PAUSE state.

However, a PAUSE frame should not affect the

transmission of a frame that has been submitted to the MAC (started Transmit out of the

MAC and can’t be interrupted). On the other hand, the AN983B shall not begin to transmit a

frame more than one Slot-Times after received a valid PAUSE frame with a non-zero

PAUSE time. If the AN983B receives a PAUSE frame with a zero PAUSE time value, then

ADMtek Inc.

www.admtek.com.tw

Rev. 1.8

AN983 数据表(PDF) 70 Page - List of Unclassifed Manufacturers

AN983 数据表(HTML) 70 Page - List of Unclassifed Manufacturers

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91

数据表下载