IP178A datasheet(19/44 Pages) ETC1

19 / 44 page

(Advance Version)

IP178A

IEEE 802.3x

The IEEE 802.3x is used for flow control in full duplex

mode if both IP178A (X_en=1) and the remote station

have IEEE802.3x capability. When the level of occupied

buffer of a port is over set threshold, it will send a

PAUSE frame with maximum delay FFFF. The remote

station will stop to transmit the next packet after

receiving the PAUSE frame. After level of the occupied

buffer is below release threshold, the port sends out a

PAUSE frame with zero delay to resume receiving the

incoming packets. The remote station is re-enable to

transmit packets after receiving the PAUSE frame with

zero delay. While level of the occupied buffer of a port is

over set threshold, IP178A re-transmits the PAUSE

frame with maximum delay to ensure the pause timer of

the remote station does not expire and begins

transmission. The IPG between PAUSE frames is

42ms(100M) or 420ms(10M).

When an incoming PAUSE frame with non-zero delay is

received, the port stops the next frame transmission and

starts its pause timer. It is re-enabled transmission

function either the pause timer is expired or a PAUSE

frame with zero delay is received. If another pause frame

is received before the timer expires, the timer will be

updated with the new value. During this period, only

PAUSE frame from IP178A will be transmitted.

PAUSE Frame Format

Destination

Source

Type

Opcode

Pause Timer

Pad

CRC

01-80-C2-00-00-01

8808

0001

FFFF(0000)

PAD with zero

CRC

6 bytes

2 bytes

2bytes

2 bytes

42 bytes

4 bytes

Preliminary, Specification subject to change without notice 19

IP178A-DS-P05

Sep. 09, 2002

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