Blue Heat/PCI User’s Manual, Connect Tech Inc. 37 Revision 0.11 Line/Bias Termination You can use jumper blocks JA, JB, JC and JD to terminate and bias TxD ±, RxD ±, RTS ±, and CTS ± on the individual RS-422/485 ports through jumper selectable 150 Ω fixed resistors. Please refer to Figure 12 for a partial schematic of the RS-422/485 circuit for the Blue Heat/PCI Opto and Figure 6 for the locations of JA, JB, JC, and JD. Figure 12: Partial schematic: Blue Heat/PCI Opto
TxD
TxD +
RxD -
TxD -
RxD +
Blue Heat/PCI Opto
RS-422/485 Line Bias/Termination
RxD
RTS
RTS +
CTS -
RTS -
CTS +
CTS
16C2850
UART
150 Ω
1.8K Ω
1.8K Ω
+5 V
150 Ω
1.8K Ω
1.8K Ω
+5 V
Optical
Isolator
Optical
Isolator
Optical
Isolator
Optical
Isolator
150 ΩJA2, JB2, JC2, JD2
150 ΩJA1, JB1, JC1, JD1
JA5, JB5, JC5, JD5
JA6, JB6, JC6, JD6
JA4, JB4, JC4, JD4
JA3, JB3, JC3, JD3

Note: Line bias/termination is jumper selectable

Example The following example shows the settings on JA, JB, JC and JD where the RS-422/485 port 1 is set for bias/termination on CTS ±, and RxD ±; the RS-422/485 port 2 is set for bias/termination on RTS ±, TxD ±, CTS ±, and RxD ±; RS-422/485 port 3 is not terminated, and the RS-422/485 port 4 is not terminated
JD1
JBJC
JD2
JD3
JD4
JD5
JD6
JD7
JD8
JD JA
COM4
JC1
JC2
JC3
JC4
JC5
JC6
JC7
JC8
COM3
JB1
JB2
JB3
JB4
JB5
JB6
JB7
JB8
COM2
JA1
JA2
JA3
JA4
JA5
JA6
JA7
JA8
COM1
RTS ± TERM
TXD ± TERM
CTS ± BIAS
CTS ± BIAS
RXD ± BIAS
RXD ± BIAS
1.

Technical Notes:

If you wish to bias/terminate CTS ± on a specific port, you must

jumper both CTS ± positions on the appropriate jumper block.

If you wish to bias/terminate RxD ± on a specific port, you must

jumper both RxD ± positions on the appropriate jumper block.

For RS-232 ports do not jumper any positions on the

appropriate JA, JB, JC and JD jumper block.