Appendix d: 20ma current loop line interface, Blue heat/pci 20ma cl – Connect Tech Blue Heat/PCI PCI Serial Communications User Manual
Page 40
Blue Heat/PCI User’s Manual, Connect Tech Inc.
Revision 0.11
40
Appendix D: 20mA Current Loop Line Interface
Blue Heat/PCI 20mA CL
The Blue Heat/PCI CL offers a 20mA Current Loop active or passive electrical interface. For
each port there is an optically isolated receiver, an optically isolated transmitter and a 20mA
current source. Optical isolation is functional in passive mode only. See
for the
schematic of the 20mA Current Loop module.
Note: The current source uses a compliance voltage of 11 or 22 volts, and the transmitter will
withstand a 27 volt drop. Please refer to the Hewlett Packard Optoelectronics Manual/Catalogue
for a complete description of HPCL 4100 and HPCL 4200 specifications.
Figure 15: Partial schematic: Blue Heat/PCI 20mA CL
51 Ohm
VF = 1.5V
-12V
RxD SRC
+12V
RxD RET
2N2907A
22K
51 Ohm
VF = 1.5V
RxD SRC
+12V
RxD RET
2N2907A
22K
+5V
+5V
+5V
3 TxD +
TxD 6
4 TxD -
HCPL
4100
5
8
HCPL
4200
8
5
6
RxD 7
1 RxD +
2 RxD -
CTS
DCD
RI
DSR
300 mA
J1, J2, J3, J4, J5, J6, J7, J8
(must jumper – see Current
Source/Voltage Selection)
To implement an optically isolated passive interface, wire the transmitter and the receiver, while
leaving the current sources unconnected. An external current source is required to implement a
passive interface.
To implement an active interface, connect a 20mA current source in series with the transmitter
and another 20mA current source in series with the receiver. Please refer to
for a
20mA Current Loop cable wiring configuration between one port of a Blue Heat/PCI CL adapter
and another port of a Blue Heat/PCI CL adapter. This example shows wiring for both active and
passive modes