
DR
AFT
DR
AFT
DRAFT
DR
D
RAFT
DRAFT
DRA
FT DRAF
D
RAFT DRAFT DRAFT DRAFT DRAFT D
DRAFT
D
RAFT DRA
FT DRAFT DRAFT DRAFT DRA
UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
122 of 808
NXP Semiconductors
UM10360
Chapter 10: LPC17xx Ethernet
11.3 Back-to-Back Inter-Packet-Gap Register (IPGT - 0x5000 0008)
The Back-to-Back Inter-Packet-Gap register (IPGT) has an address of 0x5000 0008. Its
bit definition is shown in
.
11.4 Non Back-to-Back Inter-Packet-Gap Register (IPGR - 0x5000 000C)
The Non Back-to-Back Inter-Packet-Gap register (IPGR) has an address of 0x5000 000C.
Its bit definition is shown in
11:10
-
Reserved. User software should not write ones to reserved bits. The value read
from a reserved bit is not defined.
0x0
12
NO BACKOFF
When enabled (set to ’1’), the MAC will immediately retransmit following a collision
rather than using the Binary Exponential Backoff algorithm as specified in the
Standard.
0
13
BACK PRESSURE /
NO BACKOFF
When enabled (set to ’1’), after the MAC incidentally causes a collision during back
pressure, it will immediately retransmit without backoff, reducing the chance of
further collisions and ensuring transmit packets get sent.
0
14
EXCESS DEFER
When enabled (set to ’1’) the MAC will defer to carrier indefinitely as per the
Standard. When disabled, the MAC will abort when the excessive deferral limit is
reached.
0
31:15
-
Reserved. User software should not write ones to reserved bits. The value read
from a reserved bit is not defined.
0x0
Table 108. MAC Configuration register 2 (MAC2 - address 0x5000 0004) bit description
Bit
Symbol
Function
Reset
value
Table 109. Pad operation
Type
Auto detect
pad enable
MAC2 [7]
VLAN pad
enable
MAC2 [6]
Pad/CRC
enable
MAC2 [5]
Action
Any
x
x
0
No pad or CRC check
Any
0
0
1
Pad to 60 bytes, append CRC
Any
x
1
1
Pad to 64 bytes, append CRC
Any
1
0
1
If untagged, pad to 60 bytes and append CRC. If VLAN tagged: pad to
64 bytes and append CRC.
Table 110. Back-to-back Inter-packet-gap register (IPGT - address 0x5000 0008) bit description
Bit
Symbol
Function
Reset
value
6:0
BACK-TO-BACK
INTER-PACKET-GAP
This is a programmable field representing the nibble time offset of the minimum
possible period between the end of any transmitted packet to the beginning of the
next. In Full-Duplex mode, the register value should be the desired period in
nibble times minus 3. In Half-Duplex mode, the register value should be the
desired period in nibble times minus 6. In Full-Duplex the recommended setting is
0x15 (21d), which represents the minimum IPG of 960 ns (in 100 Mbps mode) or
9.6 µs (in 10 Mbps mode). In Half-Duplex the recommended setting is 0x12 (18d),
which also represents the minimum IPG of 960 ns (in 100 Mbps mode) or 9.6 µs
(in 10 Mbps mode).
0x0
31:7
-
Reserved. User software should not write ones to reserved bits. The value read
from a reserved bit is not defined.
0x0