UM10211 - Standard ICs

NXP Semiconductors
UM10211
Chapter 11: LPC2300 Ethernet
Table 138. Non Back-to-back Inter-packet-gap register (IPGR - address 0xFFE0 000C) bit description
Bit Symbol Function Reset
value
6:0 NON-BACK-TO-BACK
INTER-PACKET-GAP PART2
This is a programmable field representing the Non-Back-to-Back
Inter-Packet-Gap. The recommended value is 0x12 (18d), which
represents the minimum IPG of 960 ns (in 100 Mbps mode) or 9.6 µs (in
10 Mbps mode).
7 - Reserved. User software should not write ones to reserved bits. The value
read from a reserved bit is not defined.
14:8 NON-BACK-TO-BACK
INTER-PACKET-GAP PART1
This is a programmable field representing the optional carrierSense
window referenced in IEEE 802.3/4.2.3.2.1 'Carrier Deference'. If carrier is
detected during the timing of IPGR1, the MAC defers to carrier. If,
however, carrier becomes active after IPGR1, the MAC continues timing
IPGR2 and transmits, knowingly causing a collision, thus ensuring fair
access to medium. Its range of values is 0x0 to IPGR2. The recommended
value is 0xC (12d)
31:15 - Reserved. User software should not write ones to reserved bits. The value
read from a reserved bit is not defined.
10.5 Collision Window / Retry Register (CLRT - 0xFFE0 0010)
The Collision window / Retry register (CLRT) has an address of 0xFFE0 0010. Its bit
definition is shown in Table 11–139.
Table 139. Collision Window / Retry register (CLRT - address 0xFFE0 0010) bit description
Bit Symbol Function Reset
value
3:0 RETRANSMISSION
MAXIMUM
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 attemptLimit to be 0xF (15d). See IEEE 802.3/4.2.3.2.5.
7:4 - Reserved. User software should not write ones to reserved bits. The value read from
a reserved bit is not defined.
13:8 COLLISION
WINDOW
This is a programmable field representing the slot time or collision window during
which collisions occur in properly configured networks. The default value of 0x37
(55d) represents a 56 byte window following the preamble and SFD.
31:14 - Reserved, user software should not write ones to reserved bits. The value read from
a reserved bit is not defined.
10.6 Maximum Frame Register (MAXF - 0xFFE0 0014)
The Maximum Frame register (MAXF) has an address of 0xFFE0 0014. Its bit definition is
shown in Table 11–140.
Table 140. Maximum Frame register (MAXF - address 0xFFE0 0014) bit description
Bit Symbol Function Reset
value
15:0 MAXIMUM FRAME
LENGTH
This field resets to the value 0x0600, which represents a maximum receive frame of
1536 octets. An untagged maximum size Ethernet frame is 1518 octets. A tagged
frame adds four octets for a total of 1522 octets. If a shorter maximum length
restriction is desired, program this 16 bit field.
31:16 - Unused 0x0
0x0
0x0
0x0
0x0
0xF
0x0
0x37
NA
0x0600
UM10211_1
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User manual Rev. 01 — 27 March 2007 145 of 613