Model 8324

RS-232 to RS-485 Interface Converter
DIN -Rail Mounted
 

Reference Manual

0315-0270 Rev. B

Printed 03.07.02

Table of Contents

1.0 Description

2.0 Operating Mode
2.1 Block Diagram
2.2 RS-485 Two-Wire Connection
2.3 RS-485 HDX operation mode

3.0 Connection/Cabling
3.1 RS-232 I/O (DCE mode)
3.2 RS-485 I/O
3.3 DIN rail mounting of Model 8324

4.0 DIP Switches
4.1 DIP-Switch S1
4.3 DIP-Switch S3
4.4 Switch Functions
4.5 Factory settings: Master Mode

5.0 Specifications
6.0 Help

 
1.0 Description

The Model 8324 RS-232 to RS-485 interface converter allows information exchange in half-duplex mode over one twisted-pair cable. It converts RS-485 signals to RS-232 signals, bi-directionally, on a DIN-Rail mounting system.

The RS-485 standard specified by the Electronic Industries Association (EIA) relates to the electrical characteristics of the generators and receivers used in a multi-point system with symmetrical or balanced digital signals. The RS-485 interface allows the user to control up to 32 devices in a half duplex via a two-wire, with one twisted pair line.
 

 
The Model 8324 has one RS-232 I/O configured in DCE mode, enabling the reception of data (on the RS-485 side) or the transmission of data towards the RS-485, over one twisted pair. The principle of the RS-485 two-wire connection involves a half-duplex transmission mode (i.e., only one device at a given time is authorized to transmit data). Because this also utilizes a polling procedure, it is also referred to as a master-slave network. The other stations (slaves) must be in stand-by mode, that corresponds to a "high impedance" state for each driver. The control of the driver is generally realized from the RTS signal, although the Model 8324 also allows control by sampling Transmit Data. This feature is described in Section 2.0, "Operating Mode." The control of devices in RS-485 mode requires multi-point software with polling sequences. The secondary stations controlled by the master station cannot transmit data unless they are selected.

Note: The two-wire RS-485 link connecting the various equipment requires a cable with at least one twisted pair, nominal impedance of 120 W and general shielding. The use of a cable with different characteristics can lead to unreliable operation, especially in cases of high data rates and long distance.

2.0 Operating Mode

2.1 Block Diagram
 

 
The Model 8324 provides opto-isolation between the RS-232 interface and the RS-485 line via optical couplers. The transmit data from the RS-232 port can be sent over the RS-485 line only if the RS-485 driver is in active mode. This active mode can be initialized either by activation of the RTS signal from the RS-232 port or by detection of transitions on the transmit data lead (Pin 2 TD). This feature enables the Model 8324 adapter to support the XON/XOFF flow control from equipment using only the TD, RD and GND.

2.2 RS-485 Two-Wire Connection

Terminating impedance
 

 
The principle of two-wire connection (one twisted pair) enables the management of up to 32 peripheral devices. The principle of an RS-485 two-wire link is based upon the use of independent transmission and reception circuits. Each link requires a terminating load on the ends of the cable. Each Model 8324 includes a switch-selectable termination. Units located at the ends of the cable should have this 120-W termination (RS-485 standard) selected.

The intermediate secondary stations can use a balancing termination by connecting a "pull-up" resistor to the negative line side of the bus and a "pull-down" resistor to the positive side of the bus, thereby forcing a zero condition on the line. The secondary station transmission circuits present the characteristic of operating in three-state mode, a high impedance state during the idle period (i.e., period of non data transfer).

The sending of data from one station can be initiated by the incoming RTS signal (Pin 4) on the RS-232 side going active, or by internal generation of a data-received signal on the RS-232 side. This second method, controlled by a microprocessor, enables the use of the Model 8324 with a simple three-wire (TD, RD and GND) RS-232 connection and XON/XOFF flow control.

2.3 RS-485 HDX operation mode

The lack of a control circuit on the RS-232 side requires that the Model 8324 take control of managing the driver for transmission of data towards the RS-485 line. Detecting a start bit sets off the driver immediately ("t0"), remaining active until a half-bit following the last stop bit. If a new start bit is detected during "t2" time, the driver is kept active until the next character and so on. The internal microprocessor controls the "t0" and "t2" times in accordance with the transmission parameters indicated by the user via the S1 DIP-switch (refer to section 4.3, "DIP-switch S3").
 

3.0 Connection/Cabling

3.1 RS-232 I/O (DCE mode)
 

3.2 RS-485 I/O
 

 
3.3 DIN rail mounting of Model 8324

Top View :

4.0 DIP Switches

The Model 8324 incorporates a micro-controller to manage the host protocols of the interface. Many of the parameters controlling the micro are established via dip switches. Some of these settings are marked "Mandatory" and should not be changed. Other user-selectable switches are appropriately marked "X."

 
4.1 DIP-Switch S1

4.3 DIP-Switch S3

Generally the use of an RS-485 interface implies controlling the half-duplex operation mode. The DIP-switch block S1 enables the selection of the operating mode and data transmission characteristics needed by the microprocessor when detecting and managing the active phases of the RS-485 transceiver (refer to section 2.3, "RS-485 HDX Operation Mode").

Transmitter Configuration S3-1 to S3-3 Baud Rate, S3-4 to S3-5 Byte Format

 
- S3-6 : OFF (ON : not allowed)
- S3-7 : OFF (ON : not allowed)
- S3-8 : OFF (ON : not allowed)

4.4 Switch Functions
 

 
4.5 Factory settings: Master Mode
 

Dark areas show switch position

5.0 Specifications

Interfaces

RS-232 (V.24) and two-wire RS-485 (EIA)/V28 (CCITT)

Transmission mode

Serial Asynchronous, HDX mode (with/without RTS signal)

Transmission speed

Transparent to 38,400 Bps

Transmission Code

Transparent

Isolation

Via opto-couplers

Power

115 VAC, 60 Hz standard, 230 VAC, 50 Hz optional

Consumption

2.5 W Maximum

Dimensions

3.1 in x 1.57 in x 3.35 in (79 mm x 40 mm x 85 mm)

Environment

Operating Temperature: 0° to 50° C

Storage Temperature: -20° to 70° C

Humidity: 10% to 90%. No condensation.

Approvals

CE marked

6.0 Help

Assistance can be obtained by visiting our Technical Support Center.
 

Warranty

TELEBYTE warrants the equipment to be free from defects in material and workmanship, under normal and proper use and in its unmodified condition, for 12 months, starting on the date it is delivered for use. TELEBYTE's sole obligation under this warranty shall be to furnish parts and labor for the repair or replacement of products found by TELEBYTE to be defective in material or workmanship during the warranty period. Warranty repairs will be performed at the point of manufacture. Equipment approved for return for warranty service shall be returned F.O.B. TELEBYTE factory and will be redelivered by TELEBYTE freight prepaid, except for non-continental U.S.A. locations. Non-continental deliveries will be sent COD freight plus import/export charges.

The above warranty is in lieu of all other warranties, expressed or implied, statutory or otherwise, including any implied warranty of merchantability or fitness for a particular purpose. TELEBYTE shall not be liable for any damages sustained by reseller or any other party arising from or relating to any equipment failure, including, but not limited to consequential damages nor shall TELEBYTE have any liability for delays in replacement or repair of equipment.

Out of warranty equipment may be returned to the Greenlawn, NY customer service facility prepaid as described above. Return shipping charges will be billed to the customer. The repaired unit will have a 90-day warranty. In those cases where "NO TROUBLE" is found, a reduced charge will be billed to cover handling, testing and packaging.

Whether in or out of warranty, a Return Material Authorization (RMA) number is necessary. Assistance can be obtained by visiting our Technical Support Center.

Document No. 0315-0270/Rev. B
 

Model	Product Info
8324