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EMAC Registers
943
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Ethernet Controller
Table 15-25. EMACCFG Register Field Descriptions (continued)
Bit
Field
Type
Reset
Description
27
TWOKPEN
R/W
0x0
IEEE 802.3as Support for 2K Packets. When set, the MAC considers
all frames, up to 2,000 bytes in length, as normal packets. This bit is
only valid when the JFEN bit is set to 0. When JFEN is set,
configuring TWOKPEN has no effect on Giant Frame status.
0x0 = If the JFEN bit is clear, the MAC considers all received frames
larger than 1,518 bytes (1522 byes tagged) as Giant Frames.
0x1 = Frames up to 2 KB are considered normal packets.If the JFEN
bit is clear, the MAC considers all received frames larger that 2K
bytes as Giant frames.
26
RESERVED
R
0x0
25
CST
R/W
0x0
CRC Stripping for Type Frames. When set, the last four bytes
(Frame Check Sequence FCS) of all frames of Ether type
((Length/Type field greater than or equal to 0x0600) are removed
before forwarding the frame to the application.
0x0 = No bytes are removed.
0x1 = The last four bytes are removed before forwarding.
24
RESERVED
R
0x0
23
WDDIS
R/W
0x0
Watchdog Disable. When this bit is set, the MAC disables the
internal watchdog counter on the receiver. The MAC can receive
frames of up to 16,384 bytes. When this bit is cleared, the MAC does
not allow more than 2,048 bytes (10,240 if JFEN is set to 1) of the
frame being received. The MAC cuts off any bytes received after
2,048 bytes.
0x0 = Watchdog counter enabled.
0x1 = Watchdog counter disabled.
22
JD
R/W
0x0
Jabber Disable. When this bit is set, the MAC disables the jabber
counter on the transmitter. The MAC can transfer frames of up to
16,384 bytes. When this bit is clear, the MAC stops transmission if
the application sends out more than 2,048 bytes of data (10,240 if
JFEN is set to 1).
0x0 = Jabber counter enabled.
0x1 = Jabber counter disabled.
21
RESERVED
R
0x0
20
JFEN
R/W
0x0
Jumbo Frame Enable. When this bit is set, the MAC allows jumbo
frames of 9,018 bytes (9,022 bytes for VLAN tagged frames) without
reporting a giant frame error in the receive frame status.
0x0 = Jumbo frames create giant frame error.
0x1 = Jumbo frames allowed without error.
19-17
IFG
R/W
0x0
Inter-Frame Gap (IFG). These bits control the minimum IFG between
frames during transmission. In half-duplex mode, the minimum IFG
can be configured only for 64 bit times (IFG = 0x4). Lower values are
not considered.
0x0 = 96 bit times
0x1 = 88 bit times
0x2 = 80 bit times
0x3 = 72 bit times
0x4 = 64 bit times
0x5 = 56 bit times
0x6 = 48 bit times
0x7 = 40 bit times
16
DISCRS
R/W
0x0
Disable Carrier Sense During Transmission. When this bit is set, the
MAC transmit module ignores carrier sense in half-duplex mode.
Thus, errors are not generated when there is a loss of carrier or no
carrier during transmission. When this bit is clear, the MAC
transmitter generates errors because of carrier sense and can even
abort the transmissions.
0x0 = Generate errors for carrier sense errors.
0x1 = Ignore carrier sense errors.