GW-7238D J1939 to MBTCP Server / MBRTU Slave Gateway User’s Manual (Ver.1.1, May. 2013) ---
13
Moreover, to minimize the voltage drop on long distance, the terminal
resistance should be higher than the value defined in the ISO 11898-2.
Table 2-4 may be used as a reference.
Table 2-4: Relation between bus cable and length
Bus Cable Parameters
Bus Length
(meter)
Length Related
Resistance
(m
Ω
/m)
Cross Section
(Type)
Terminal
Resistance
(
Ω
)
0~40
70
0.25(23AWG)~
0.34mm
2
(22AWG)
124
(0.1%)
40~300
< 60
0.34(22AWG)~
0.6mm
2
(20AWG)
127
(0.1%)
300~600
< 40
0.5~0.6mm
2
(20AWG)
150~300
600~1K
< 20
0.75~0.8mm
2
(18AWG)
150~300
Therefore, the GW-7238D module supplies a jumper for users to
connect the terminator resistor or not. If users want to use this terminator
resistor, please open the GW-7238D cover and use the JP3 jumper to
activate the 120
Ω
terminator resistor built in the system, as in the figure 2-
10. Note that the default setting is active. And about the J3 jumper setting,
please refer the table 2-5.
Figure2-10:XC100 I/O expansion board layout (Rev1.8 / Rev1.9)