10BASE-T : link integrity test (LIT) or normal link pulses (NLP) in Autonegotiation.
These pulses are sent by a device when it is not sending or receiving any data.
positive-only electrical pulses of a duration of 100 ns, generated at intervals of 16 ms.
neither a packet nor one of the pulses are received for 50-150 ms A device detects the failure of the link.
Autonegotiation : fast link pulse (FLP) , 33 pulses, unipolar, positive-only, and of the duration of 100 ns.
17 pulses at distance 125 µs represents clock. in the middle of each set of two consecutive pulses may be 1 or 0 which represents information. 16 1 or 0 represents a word of 16 bits called link code word (LCW) or page. First bit is sent first.
FLP is not recognized as a valid normal link pulse. a 10BASE-T device receiving it from an autonegotiation device will detect a failure of the link.
the 10BASE-T device keeps sending normal link pulses or transmitting packets. The autonegotiation device, upon receiving them, switches to 10BASE-T half-duplex mode then .
link code word formates:
0–4: selector field: EEE 802.3 and IEEE 802.9
5–12: technology ability field (bit 0 ~ bit 7)
- bit 0: device supports 10BASE-T
- bit 1: device supports 10BASE-T in full duplex
- bit 2: device supports 100BASE-TX
- bit 3: device supports 100BASE-TX in full duplex
- bit 4: device supports 100BASE-T4
- bit 5: pause
- bit 6: asymmetric pause for full duplex
- bit 7: reserved
14: acknowledgment: three identical base code words detected, then set this bit to 1 to indicate the correct reception
15: next page: 1 to indicate indicate the intention of sending other link code words after the base link code word;
The first of 3 link code word which is called base link code word( or first page). 10BASE-T, 100BASE-TX and 100BASE-T4 is detected in first page and for 100M only base page is enough.
Upon receiving these three identical copies, the device sends a link code word with the acknowledge bit set to one from six times to eight times.
Giga bit ethernet: 3 pages is required.
The additional pages are of two kinds: message pages and unformatted pages.
first eleven bits are data, 12~14 indicates this page is message page or an unformatted page, 15 indicates if there's an additional page.
The 1000BASE-T :
1. first page
2. unformatted page - contains 10-bit word data, called a master-slave seed value.
3. message page - indicates supported modes and master-slave device as following items,
- half duplex capability
- whether the device is single port or multiport
- whether master/slave is manually configured or not
- whether the device is manually configured as master or slave
- 1000BASE-T full duplex
- 1000BASE-T half duplex
- 100BASE-T2 full duplex
- 100BASE-TX full duplex
- 100BASE-T2 half duplex
- 100BASE-T4
- 100BASE-TX half duplex
- 10BASE-T full duplex
- 10BASE-T half duplex
Duplex mismatch
When a device set to autonegotiation is connected to a device that is not using autonegotiation, the autonegotiation process fails. The autonegotiating end of the connection is still able to correctly detect the speed of the other end, but cannot detect the duplex mode. The standard requires the use of half duplex in these conditions. Therefore, the autonegotiating end of the connection uses half duplex while its peer is locked at full duplex, and this is a duplex mismatch.568A + 568A 或 568B + 568B這是一般平行線的做法
568A + 568B 是跳線
而你應該用平行線。
