SMSC LAN9311 User Manual

Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface

Revision 1.4 (08-19-08)

58

SMSC LAN9311/LAN9311i

 

Each switch fabric port (0,1,2) is provided with two flow control enable inputs per port, one for
transmission and one for reception. Flow control on transmission allows the transmitter to generate
back pressure in half-duplex mode, and pause packets in full-duplex. Flow control in reception enables
the reception of pause packets to pause transmissions.

The state of these enables is based on the state of the ports duplex and Auto-negotiation settings and
the values of the corresponding Manual Flow Control register (

, 

 details the switch fabric flow control

enable logic. 

When in half-duplex mode, the transmit flow control (back pressure) enable is determined directly by
the BP_EN_x bit of the ports manual flow control register. When Auto-negotiation is disabled, or the
MANUAL_FC_x bit of the ports manual flow control register is set, the switch port flow control enables
during full-duplex are determined by the TX_FC_x and RX_FC_x bits of the ports manual flow control

Idle

Write 

Command 

Register

Read 

Command 

Register

Read Data 

Register

CSR_BUSY = 0

CSR_BUSY = 1

Idle

Write 

Command 

Register

Read 

Command 

Register

CSR_BUSY = 0

CSR_BUSY = 1

Write 

Command 

Register

Read Data 

Register

last 

data?

Yes

No

Read Data 

Register

min wait period

min wait period

min wait period