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AT32F435/437
Series Reference Manual
2022.11.11
Page 615
Rev 2.03
This field defines the threshold of the Pause timer.
The threshold values should always be less than the
Pause time defined in the [31: 16] bit. For example, if PT
= 100H (256 slot times), and PLT = 01, then a second
Pause frame is automatically transmitted if initiated at 228
(256-28) slot times after the first Pause frame is
transmitted.
Threshold selection as follows:
00: Pause time minus 4 slot times (PT minus 4 slot times)
01: Pause time minus 28 slot times (PT minus 28 slot
times)
10: Pause time minus 144 slot times (PT minus 144 slot
times)
11: Pause time minus 256 slot times (PT minus 256 slot
times)
Slot time is defined as the time taken to transmit 512 bits
(64 bytes) on the MII interface.
Bit 3
DUP
0x0
rw
Detect Unicast Pause Frame
The Pause frame with a unique multicast address as
specified in the IEEE 802.3 will be processed. When this
bit is set, the MAC detects the Pause frames with a unicast
address specified in the MAC address0 high and MAC
address0 low registers.
When this bit is cleared, the MAC detects only a Pause
frame with a unique multicast address.
Note: If the multicast address of the received frame does
not match the unique multicast address, the MAC will not
process the Pause frame.
Bit 2
ERF
0x0
rw
Enable Receive Flow control
When this bit is set, the MAC decodes the received Pause
frame and disables the transmitter for a period of time.
When this bit is cleared, the decode function of the Pause
frame is disabled.
Bit 1
ETF
0x0
rw
Enable Transmit Flow control
In full-duplex mode, when this bit is set, the MAC enables
the flow control operation to transmit Pause frames. When
this bit is cleared, the flow control of the MAC is disabled,
and the MAC does not transmit any Pause frames.
In half-duplex mode, when this bit is set, the MAC enables
the back-pressure feature. When this bit is cleared, the
back-pressure feature is disabled.
Bit 0
FCB/BPA
0x0
rw1c/rw
Flow Control Busy/Back Pressure Activate
In full-duplex mode, this bit initiates a Pause frame; in half-
duplex mode, the back-pressure feature is activated if the
TFE bit is set.
In full-duplex mode, this bit is read as 1'b0 before writing
to the EMAC_MACFCTRL register. The application must
set this bit to 1'b1 to initiate a Pause frame. During a
control frame transmission, this bit remains set, indicating
that a frame transmission is in progress. After the
completion of the Pause frame, the MAC resets this bit to
1'b0. The Ethernet MAC flow control register
(EMAC_MACFCTRL) should not be written until this bit is
cleared.
In half-duplex mode, when this bit is set (and the TFE is
set), the back-pressure feature is activated by the MAC.
During back pressure, when the MAC receives a new
frame, the transmitter starts sending a JAM mode,
resulting a collision. When the MAC is configured to full-
duplex mode, the back-pressure (BAP) function is
automatically disabled.