lan9311 Standard Microsystems Corp., lan9311 Datasheet - Page 58

• Manufacturer Part Number: lan9311
• Description: Lan9311/lan9311i Two Port 10/100 Managed Ethernet Switch With 16-bit Non-pci Cpu Interface
• Manufacturer: Standard Microsystems Corp.

Revision 1.2 (04-08-08)
6.2.3
Flow Control Enable Logic
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
(MANUAL_FC_1),
Manual Flow Control Register
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
Figure 6.2 Switch Fabric CSR Read Access Flow Diagram
CSR Read
Port 2 Manual Flow Control Register
Read Data
Command
Command
Register
Register
Register
Read
Write
Idle
CSR_BUSY = 0
min wait period
CSR_BUSY = 1
(MANUAL_FC_MII)).
DATASHEET
58
Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface
min wait period
CSR Read Auto
Increment /
Decrement
Read Data
Command
Command
Command
Register
Register
Register
Register
Write
Read
Write
data?
Idle
last
Table 6.1
CSR_BUSY = 0
Yes
No
(MANUAL_FC_2), or
CSR_BUSY = 1
min wait period
(Port 1 Manual Flow Control Register
details the switch fabric flow control
Read Data
Register
SMSC LAN9311/LAN9311i
Port 0(Host MAC)
Datasheet