LAN9211 datasheet(99/147 Pages) SMSC

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High-Performance Small Form Factor Single-Chip Ethernet Controller with HP Auto-MDIX Support

Datasheet

SMSC LAN9211

Revision 2.9 (03-01-12)

DATASHEET

5.3.22

AFC_CFG – Automatic Flow Control Configuration Register

This register configures the mechanism that controls both the automatic, and software-initiated

transmission of pause frames and back pressure.

Note: The LAN9211 will not transmit pause frames or assert back pressure if the transmitter is

disabled.

Offset:

ACh

Size:

32 bits

BITS

DESCRIPTION

TYPE

DEFAULT

31:24

Reserved

23:16

Automatic Flow Control High Level (AFC_HI). Specifies, in multiples of

64 bytes, the level at which flow control will trigger. When this limit is

reached the chip will apply back pressure or will transmit a pause frame as

programmed in bits [3:0] of this register.

During full-duplex operation only a single pause frame is transmitted when

this level is reached. The pause time transmitted in this frame is

programmed in the FCPT field of the FLOW register in the MAC CSR space.

During half-duplex operation each incoming frame that matches the criteria

in bits [3:0] of this register will be jammed for the period set in the

BACK_DUR field.

R/W

00h

15:8

Automatic Flow Control Low Level (AFC_LO). Specifies, in multiples of

64 bytes, the level at which a pause frame is transmitted with a pause time

setting of zero. When the amount of data in the RX data FIFO falls below

this level the pause frame is transmitted. A pause time value of zero

instructs the other transmitting device to immediately resume transmission.

The zero time pause frame will only be transmitted if the RX data FIFO had

reached the AFC_HI level and a pause frame was sent. A zero pause time

frame is sent whenever automatic flow control in enabled in bits [3:0] of this

Note:

When automatic flow control is enabled the AFC_LO setting must

always be less than the AFC_HI setting.

R/W

00h

7:4

Backpressure Duration (BACK_DUR). When the LAN9211 automatically

asserts back pressure, it will be asserted for this period of time. This field

has no function and is not used in full-duplex mode. Please refer to

Table 5.5, describing Backpressure Duration bit mapping for more

information.

R/W

Flow Control on Multicast Frame (FCMULT). When this bit is set, the

LAN9211 will assert back pressure when the AFC level is reached and a

multicast frame is received. This field has no function in full-duplex mode.

R/W

Flow Control on Broadcast Frame (FCBRD). When this bit is set, the

LAN9211 will assert back pressure when the AFC level is reached and a

broadcast frame is received. This field has no function in full-duplex mode.

R/W

Flow Control on Address Decode (FCADD). When this bit is set, the

LAN9211 will assert back pressure when the AFC level is reached and a

frame addressed to the LAN9211 is received. This field has no function in

full-duplex mode.

R/W

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