LAN9116 Datasheet, PDF (80/109 Pages) SMSC Corporation – Highly Efficient Single-Chip 10/100 Non-PCI Ethernet Controller

LAN9116
5.4.7 MII_DATA—MII DATA REGISTER
Offset:
7
Attribute:
R/W
Default Value:
00000000h
Size:
32 bits
This register contains either the data to be written to the PHY register specified in the MII Access Register, or the read
data from the PHY register whose index is specified in the MII Access Register.
Bits
31-16
15-0
Reserved
Description
MII Data. This contains the 16-bit value read from the PHY read operation or the 16-bit data value to
be written to the PHY before an MII write operation.
5.4.8 FLOW—FLOW CONTROL REGISTER
Offset:
8
Attribute:
R/W
Default Value:
00000000h
Size:
32 bits
This register controls the generation and reception of the Control (Pause command) frames by the MAC’s flow control
block. The control frame fields are selected as specified in the 802.3x Specification and the Pause-Time value from this
register is used in the “Pause Time” field of the control frame. In full-duplex mode the FCBSY bit is set until the control
frame is transferred onto the cable. In half-duplex mode FCBSY is set while back pressure is being asserted. The host
has to make sure that the Busy bit is cleared before writing the register. The Pass Control Frame bit (FCPASS) does
not affect the sending of the frames, including Control Frames, to the Application Interface. The Flow Control Enable
(FCEN) bit enables the receive portion of the Flow Control block.
This register is used in conjunction with the AFC_CFG register in the Slave CSRs to configure flow control. Software
flow control is initiated using the AFC_CFG register.
Note: The LAN9116 will not transmit pause frames or assert back pressure if the transmitter is disabled.
Bits
31-16
15-3
2
1
Description
Pause Time (FCPT). This field indicates the value to be used in the PAUSE TIME field in the control
frame. This field must be initialized before full-duplex automatic flow control is enabled.
Reserved
Pass Control Frames (FCPASS). When set, the MAC sets the Packet Filter bit in the Receive packet
status to indicate to the Application that a valid Pause frame has been received. The Application must
accept or discard a received frame based on the Packet Filter control bit. The MAC receives, decodes
and performs the Pause function when a valid Pause frame is received in Full-Duplex mode and when
flow control is enabled (FCE bit set). When reset, the MAC resets the Packet Filter bit in the Receive
packet status.
The MAC always passes the data of all frames it receives (including Flow Control frames) to the
Application. Frames that do not pass Address filtering, as well as frames with errors, are passed to
the Application. The Application must discard or retain the received frame’s data based on the received
frame’s STATUS field. Filtering modes (Promiscuous mode, for example) take precedence over the
FCPASS bit.
Flow Control Enable (FCEN). When set, enables the MAC Flow Control function. The MAC decodes
all incoming frames for control frames; if it receives a valid control frame (PAUSE command), it
disables the transmitter for a specified time (Decoded pause time x slot time). When reset, the MAC
flow control function is disabled; the MAC does not decode frames for control frames.
Note: Flow Control is applicable when the MAC is set in Full Duplex Mode. In Half-Duplex mode,
this bit enables the Backpressure function to control the flow of received frames to the MAC.
DS00002268A-page 80
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