lan9303m Standard Microsystems Corp., lan9303m Datasheet - Page 69

• Manufacturer Part Number: lan9303m
• Description: Small Form Factor Three Port 10/100 Managed Ethernet Switch With Dual Mii/rmii/turbo Mii
• Manufacturer: Standard Microsystems Corp.

Small Form Factor Three Port 10/100 Managed Ethernet Switch with Dual MII/RMII/Turbo MII
Datasheet
SMSC LAN9303M/LAN9303Mi
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 port’s duplex and Auto-negotiation settings and
the values of the corresponding Manual Flow Control register
(MANUAL_FC_1),
Control Register
When in half-duplex mode, the transmit flow control (back pressure) enable is determined directly by
the BP_EN_x bit of the port’s manual flow control register. When Auto-negotiation is disabled, or the
MANUAL_FC_x bit of the port’s 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 port’s manual flow control
register. When Auto-negotiation is enabled and the MANUAL_FC_x bit is cleared, the switch port flow
control enables during full-duplex are determined by Auto-negotiation.
Figure 6.2 Switch Fabric CSR Read Access Flow Diagram
(MANUAL_FC_0)).
CSR Read
Port 2 Manual Flow Control Register
Read Data
Command
Command
Register
Register
Register
Read
Write
Idle
CSR_BUSY = 0
CSR_BUSY = 1
DATASHEET
Table 6.1
69
CSR Read Auto
details the Switch Fabric flow control enable logic.
Increment /
Decrement
Read Data
Command
Command
Command
Register
Register
Register
Register
Write
Read
Write
data?
Idle
last
CSR_BUSY = 0
Yes
(MANUAL_FC_2), or
No
CSR_BUSY = 1
(Port 1 Manual Flow Control Register
Read Data
Register
Port 0 Manual Flow
Revision 1.3 (08-27-09)