755
/
838
Nations Technologies Inc.
Tel
：
+86-755-86309900
：
Address: Nations Tower, #109 Baoshen Road, Hi-tech Park North.
Nanshan District, Shenzhen, 518057, P.R.China
Bit field
Name
Description
6
Reserved
Reserved, the reset value must be maintained.
5:4
PLT[1:0]
PAUSE low threshold.
These bits set the timer threshold for automatic retransmission of PAUSE frames. This
threshold should be greater than 0 and less than the pause time defined by these bits in
ETH_MACFLWCTRL.PT[15:0]. The low threshold is calculated as PT - PLT. For
example, PT = 0x80 (128 time slots), PLT = 0x1 (28 time slots), then the second
PAUSE frame will be automatically retransmit 100 (128-28) time slots after the first
PAUSE frame is transmitted.
00: Pause time - 4 time slots
01: Pause time - 28 time slots
10: Pause time - 144 time slots
11: Pause time - 256 time slots
Note: A time gap refers to the time it takes for the MII interface to send 512 bits (64
bytes) of data.
3
UP
Unicast PAUSE frame detection.
0: MAC only receives PAUSE frames that conform to the unique multicast address
defined by the IEEE802.3 specification.
1: In addition to PAUSE frames with unique multicast addresses, MAC also uses the
MAC address 0 to detect PAUSE frames.
2
RFE
Receive flow control enable bit.
When this bit is set to 1, MAC will turn off the transmitter for the specified time (the
value of the Pause Time field in the received frame).
0: MAC does not parse PAUSE frames.
1: MAC parses and processes the received PAUSE frame.
1
TFE
Transmit flow control enable bit.
In full-duplex mode, this bit is 1 to indicate that MAC can transmit PAUSE frames,
and this bit is cleared to 0 to indicate that PAUSE frames are not transmitted.
In half-duplex mode, this bit is 1 to indicate that MAC enables the back pressure
function, and this bit is cleared to 0 to indicate that the back pressure function is
turned off.
0: MAC disables transmit flow control function.
1: MAC enables transmit flow control function.
0
FCB_BPA
Flow control busy/back pressure active.
In full-duplex mode, this bit can transmit PAUSE frames; in half-duplex mode, when
ETH_MACFLWCTRL.TFE is set, this bit can activate the back pressure function.
In full-duplex mode, the application should ensure that this bit is 0 before writing to
the ETH_MACFLWCTRL register. After this bit is set to 1, MAC will transmit a
PAUSE frame to the interface. During the process of transmit the control frame, the
bit is always 1, and MAC resets this bit to 0 after the PAUSE control frame is
transmitted.
In half-duplex mode, setting this bit to 1 activates the backpressure function. When
the backpressure function is valid, if MAC receives a new frame, it will transmit a
