RS232 CURRENT LOOP CONVERTER

The RS232 current loop converter provides an expandable current loop communication for standard RS232 interface.

The features of RS232 current loop converter are :
Standard EIA of RS232C communication protocol.
Passive or active current loop selectable.
One DB-25 Male RS232 connector.
Terminal block connector for long haul cable.
DCE, DTE or loopback selectable.
4 wire full duplex or 2 wire half duplex selectable.
Using DC 9V external power or supported by pin 9 of RS232C.
One Pair (two converters) is needed for two connected devices.
20mA or 60mA selectable.
Compact size.

The package contains:

Two (or One) RS232 current loop converters.
User's manual.

Hardware configuration:
1. Block Diagram
Observe the figure shown in the following, the RS232 current loop converter contains five switches, one terminal block, and one RS232 DB-25 male connector.

2. Switch Setting
    1.  SW1 (device mode selection)
DCE
DTE
The SW1 is used to select device mode.

CDE: The RS232 Current loop converter is set to DCE mode, and it must be connected to DTE device.
DTE: The RS232 Current loop converter is set to DTE mode, and it must be connected to DCE device.
    2.  SW2 (active current selection)
20mA
60mA
The SW2 is used to select Tx active current.

    3.  SW3 (transmit/receive mode selection)
Full Duplex
Half Duplex
The SW3 is used to select full duplex, half duplex for transmit or receive mode.

    4.  SW4 (Tx passive or active selection)
Passive
Active
The SW4 is used to select Tx passive or active.

    5.  SW5 (Rx passive or active selection)
Passive
Active
The SW5 is used to select Rx passive or active.

3.  Termianal Block
1
 		2
 		3
 		4
Tx2
 		Tx1
 		Rx1
 		Rx2

The terminal block is used to connect two RS232 current loop converters. The signal assignment is shown in the follow.
Connector
 		Name
 		Description
#1
 		Tx2
 		Tx current out
#2
 		Tx1
 		Tx current in
#3
 		Rx1
 		Rx current in
#4
 		Rx2
 		Rx current out

For full duplex application, please connect it as figure below.
Tx2
 1----------3
 Rx1
Tx1
 2----------4
 Rx2
Rx1
 3----------1
 Tx2
Rx2
 4----------2
 Tx1
4. Signal Asssignments for DB25

A. DTE mode (standard)
Pin
 		Name
 		Descripton
 		Direction
1
 		GND
 		Chassis Ground
 		Common
2
 		Tx
 		Transmit Data
 		Output
3
 		Rx
 		Receive Data
 		Input
4
 		RTS
 		Request to Send
 		Output
5
 		CTS
 		Clear to Send
 		Input
6
 		DSR
 		Data Set Ready
 		Input
7
 		SG
 		Signal Ground
 		Common
8
 		DCD
 		Data Carrier Detect
 		Input
20
 		DTR
 		Data Termianal Ready
 		Output

B. DCE mode
Pin
 		Name
 		Descripton
 		Direction
1
 		GND
 		Chassis Ground
 		Common
2
 		Rx
 		Receive Data Input
3
 		Tx
 		Transmit Data Output
4
 		CTS
 		Clear to Send Input
5
 		RTS
 		Request to Send Output
6
 		DTR
 		Data Termianal Ready Output
7
 		SG
 		Signal Ground
 		Common
8
 		DCD
 		Data Carrier Detect
 		Input
20
 		DSR
 		Data Set Ready Input
* The pin 4 (CTS) and pin 5 (RTS) are shorted together, and the pin 6 (DTR) and pin 20 (DSR) are shorted together in this converter.
* Some applications need short pin 6 (DTR) and pin 8 (DCD).

DEVICE CONNECTION:
1. Installation:
To use RS232 current loop converter, you must connect it by 4 wire line (24 AWG two twisted pairs), then connect both DB-25 male connector to PC or devices (we call DEVICE in the follow). Please noto that, you must set DCE or DTE mode correctly, otherwise it can not work. Suppose the DEVICE is DTE mode, you must set the RS232 current loop converter to DCE, otherwise if the DEVICE is DCE mode, you must set the RS232 current loop converter to DTE.

The full duplex connection of two RS232 current loop converters are shown in the follow.
If needed, plug in power adapter to RS232 current loop converter.

2. Loop Back Test
To test the RS232 current loop converter, please follow the steps:
1.  Set SW1 to DCE. (suppose RS232 port of your computer is DTE)
2.  Connect Tx2(#1) to Rx1(#3).
3.  Connect 50 to 100 OHM resistor from Tx1(#2) to Rx2(#4).
4.  Set the SW4 to Tx active and SW5 to Rx passive.
5.  Set the SW3 to full duplex.
6.  Run CURTEST.EXE program (which is in the distribution diskette).
7.  Key in data, you may see the key in data are shown in the monitor.

NOTE
* Do not forget to connect resistor in this test stage, otherwise it will damage the devices.
* You may set SW4 to Tx passive and SW5 to Rx active, to tesst another function.

3. Hardware Connection
Inthe following, we will introduce how to connect DB-25 from computerto computer/device, and also show the signal flow of both RS232 current loop converters.
A. DCE Mode
B.  DTE Mode
3.  Full Duplex
Side1
 		Side2
DTE or DCE
 		DTE or DCE
Full Duplex
 		Full Duplex
or
 		Tx Active
Rx Active
Tx Passive
Rx Passive
Tx Passive
Rx passive
Tx Active
Rx Active
or
 		20mA
60mA
20mA
60mA
* To select DTE or DCE, please see the section of DTE mode and DCE mode.

C.  Simplex Application
The side 1 is set to receiver and the side 2 is set to sender.

Side1
 		Side2
DTE or DCE
 		DTE or DCE
Full Duplex
 		Full Duplex
Tx Active
Rx Active
 		Tx Passive
Rx passive
or
 		20mA
60mA
20mA
60m
D.  Half Duplex Application
Side1
 		Side2
DTE or DCE
 		DTE or DCE
Half Duplex
 		Half Duplex
or
 		20mA
60mA
20mA
60m

Case 1:
Side 1 is sender, and side 2 is receiver.
Side 1
 		Side 2
Tx Active
 		Tx Passive
Rx Passive
 		Rx Passive
Case 2:
Side 2 is sender, and side 1 is receiver.
Side 1
 		Side 2
Tx Passive
 		Tx Active
Rx Passive
 		Rx Passive

Catalog
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Manual
 Converter
Cables Information
Test Tool & Sample Code
Diagram
UARTs &Line Driver