Ethernet MAC
UG0331 User Guide Revision 15.0
404
[15:8]
MINIMUM IFG
ENFORCEMENT
0x50
This programmable field represents the minimum size of
management gap (IFG) to enforce between frames
(expressed in bit times).
A frame whose IFG is less than the programmed minimum
IFG enforcement value is dropped. The default setting of
0x50 represents half of the nominal minimum IFG which is
160 bits.
7
Reserved
0x0
Reserved
[6:0]
BACK-TO-BACK INTER-
PACKET-GAP
0x60
This programmable field represents the IPG between Back-
to-Back packets (expressed in bit times). This is the IPG
parameter used exclusively in full-duplex mode when two
transmit packets are sent back-to-back. Set this field to the
desired number of bits. The default setting of 0x60
represents the minimum IPG of 96 bits.
Table 350 •
HALF_DUPLEX
Bit Number Name
Reset
Value
Description
[31:24]
Reserved
0x0
Reserved
[23:20]
ALTERNATE BINARY
EXPONENTIAL BACKOFF
TRUNCATION
0xA
This field is used when ALTERNATE BINARY EXPONENTIAL
BACKOFF ENABLE is set. The value programmed is substituted
for the Ethernet standard value of ten. Default is ‘0xA’.
19
ALTERNATE BINARY
EXPONENTIAL BACKOFF
ENABLE
0x0
Setting this bit configures the Tx MAC to use the ALTERNATE
BINARY EXPONENTIAL BACKOFF TRUNCATION setting
instead of the 802.3 standard tenth collision. Clearing this bit
causes the Tx MAC to follow the standard binary exponential
backoff rule.
18
BACKPRESSURE NO
BACKOFF
0x0
Setting this bit configures the Tx MAC to immediately re-transmit
following a collision during back pressure operation. Clearing
this bit causes the Tx MAC to follow the binary exponential
backoff rule.
17
NO BACKOFF
0x0
Setting this bit configures the Tx MAC to immediately re-transmit
following a collision. Clearing this bit causes the Tx MAC to
follow the binary exponential backoff rule.
16
EXCESSIVE DEFER
0x1
Setting this bit configures the Tx MAC to allow the transmission
of a packet that has been excessively deferred. Clearing this bit
causes the Tx MAC to abort the transmission of a packet that
has been excessively deferred.
[15:12]
RETRANSMISSION
MAXIMUM
0xF
This is a programmable field specifying the number of
retransmission attempts following a collision before aborting the
packet due to excessive collisions. The standard specifies the
maximum number of attempts to be 0xF (15d).
Table 349 •
IFG
(continued)
Bit Number Name
Reset
Value
Description