Mac configuration register #2 – Digi NS9750 User Manual
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E t h e r n e t C o m m u n i c a t i o n M o d u l e
MAC Configuration Register #2
Address: A060 0404
MAC Configuration Register #2 provides additional bits that control functionality
within the Ethernet MAC block.
Register bit assignment
Bits
Access
Mnemonic
Reset
Definition
D31:15
N/A
Reserved
N/A
N/A
D14
R/W
EDEFER
0
Excess deferral
0
The MAC aborts when the excessive deferral limit is
reached (that is, 6071 nibble times in 100 Mbps mode
or 24,287 bit times in 10 Mbps mode).
1
Enables the MAC to defer to carrier indefinitely, as
per the 802.3u standard.
D13
R/W
Not used
0
Always write to 0.
D12
R/W
NOBO
0
No backoff
When this bit is set to 1, the MAC immediately retransmits
following a collision, rather than using the binary
exponential backoff algorithm (as specified in the 802.3u
standard).
D11:10
N/A
Reserved
N/A
N/A
D09
R/W
LONGP
0
Long preamble enforcement
0
Allows any length preamble (as defined in the 802.3u
standard).
1
The MAC allows only receive frames that contain
preamble fields less than 12 bytes in length.
Table 212: MAC Configuration Register #2
Reserved
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
31
29
28
27
26
25
24
23
22
21
20
19
18
17
16
30
Reserved
Rsvd
EDE
FER
LONGP PUREP
CRCEN
Not
used
HUGE
Not
used
FULLD
Not
used
NOBO
AUTOP VLANP PADEN