4
Table 3 RJ-45 MDI interface pinouts
Pin
10Base-T/100Base-TX
1000Base-T
Signal
Function
Signal
Function
1
Tx+
Send data
BIDA+
Bi-directional data cable A+
2
Tx-
Send data
BIDA-
Bi-directional data cable A-
3
Rx+
Receive data
BIDB+
Bi-directional data cable B+
4
Reserved
N/A
BIDC+
Bi-directional data cable C+
5
Reserved
N/A
BIDC-
Bi-directional data cable C-
6
Rx-
Receive data
BIDB-
Bi-directional data cable B-
7
Reserved
N/A
BIDD+
Bi-directional data cable D+
8
Reserved
N/A
BIDD-
Bi-directional data cable D-
Table 4 RJ-45 MDI-X interface pinouts
Pin
10Base-T/100Base-TX
1000Base-T
Signal
Function
Signal
Function
1
Rx+
Receive data
BIDB+
Bi-directional data cable B+
2
Rx-
Receive data
BIDB-
Bi-directional data cable B-
3
Tx+
Send data
BIDA+
Bi-directional data cable A+
4
Reserved
N/A
BIDD+
Bi-directional data cable D+
5
Reserved
N/A
BIDD-
Bi-directional data cable D-
6
Tx-
Send data
BIDA-
Bi-directional data cable A-
7
Reserved
N/A
BIDC+
Bi-directional data cable C+
8
Reserved
N/A
BIDC-
Bi-directional data cable C-
To ensure normal communication, the pins for sending data on one port should correspond to the
pins for receiving data on the peer port. When both of the ports on the two devices are MDI or MDIX,
a crossover Ethernet cable is needed. When one port is MDI and the other is MDIX, a
straight-through Ethernet cable is needed.
If an RJ-45 Ethernet interface with MDI/MDIX autosensing enabled can automatically negotiate pin
roles. The RJ-45 Ethernet interfaces support MDI/MDIX. By default, MDI/MDIX is enabled on a port.
Making an Ethernet twisted pair cable
1.
Cut the cable to a required length with the crimping pliers.
2.
Strip off an appropriate length of the cable sheath. The length is typically that of the RJ-45
connector.
3.
Untwist the pairs so that they can lie flat, and arrange the colored wires based on the wiring
specifications.
4.
Cut the top of the wires even with one another. Insert the wires into the RJ-45 end and make
sure the wires extend to the front of the RJ-45 end and make good contact with the metal
contacts in the RJ-45 end and in the correct order.
5.
Crimp the RJ-45 connector with the crimping pliers until you hear a click.
