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EMAC Registers
1026
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Ethernet Controller
Table 15-85. EMACDMAOPMODE Register Field Descriptions (continued)
Bit
Field
Type
Reset
Description
20
FTF
R/W
0x0
Flush Transmit FIFO. This bit is cleared internally when the flushing
operation is completed. This register should not be written to until
the FTF bit is cleared. The data which has already been accepted by
the MAC transmitter is not flushed. It is scheduled for transmission
and results in underflow and runt frame transmission. The flush
operation is complete only when the TX FIFO is emptied of its
contents and all the pending Transmit Status of the transmitted
frames are accepted by the host.
0x0 = This bit indicated normal operation or that the flushing
operation has completed.
0x1 = The transmit FIFO controller logic is reset to its default values
and thus all data in the TX FIFO is lost or flushed.This bit is cleared
internally when the flushing operation is complete.
19-17
RESERVED
R
0x0
16-14
TTC
R/W
0x0
Transmit Threshold Control. These bits control the threshold level of
the TX/RX Controller Transmit FIFO. Transmission starts when the
frame size within the TX/RX Controller Transmit FIFO is larger than
the threshold. In addition, full frames with a length less than the
threshold are also transmitted. These bits are used only when Bit 21
(TSF) is reset.
0x0 = 64 bytes
0x1 = 128 bytes
0x2 = 192 bytes
0x3 = 256 bytes
0x4 = 40 bytes
0x5 = 32 bytes
0x6 = 24 bytes
0x7 = 16 bytes
13
ST
R/W
0x0
Start or Stop Transmission Command.
When this bit is set, transmission is placed in the running state. The
DMA attempts to acquire the descriptor from the Transmit Descriptor
List. Descriptor acquisition is attempted from the current position in
the list, which is the Transmit List Base Address set by Transmit
Descriptor List Address (EMACTXDLADDR) register, or from the
position retained when transmission was stopped previously.
If the DMA does not own the current descriptor, transmission enters
the suspended state and bit[2] (Transmit Buffer Unavailable, TU) of
the MAC DMA Raw Interrupt Status Register (EMACDMARIS) is set.
The Start Transmission command is effective only when
transmission is stopped. If the command is issued before setting
EMACTXDLADDR, then the DMA behavior is unpredictable.
When this bit is cleared, the transmission process is placed in the
Stopped state after completing the transmission of the current frame.
The Next Descriptor position in the Transmit List is saved, and it
becomes the current position when transmission is restarted. To
change the list address, you need to program EMACTXDLADDR
with a new value when this bit is reset. The new value is considered
when this bit is set again. The stop transmission command is
effective only when the transmission of the current frame is complete
or the transmission is in the Suspended state.
0x0 = Transmission process is placed in the stopped state after
completing the transmission of the current frame. The Next
Descriptor position in the Transmit List is saved, and it becomes the
current position when transmission is restarted.
0x1 = Transmission is placed in the running state, and the DMA
checks the transmit list at the current position for a frame to be
transmitted.
12-8
RESERVED
R
0x0