Interface Conversion

RS232 to RS422 conversion, self-powered inline

For a PC with a 9-way RS232 port:

K2 (non isolated). RTS and/or DTR signals should be at the HIGH level to power the device.

K3 (isolated). RTS and/or DTR signals should be at the HIGH level to power the device.

For a PC with 25-way RS232 port:

K422-ISOL (isolated). RTS and/or DTR signals should be at the HIGH level to power the device.

RS232 to RS422 conversion, externally powered DIN rail

For any RS232 device, data transparent:

KD485-STD (isolated). Requires +7V to +35V DC power.

RS232 to RS485 (4-wire) conversion for Master use, self-powered

For a PC with a 9-way RS232 port:

K2 (non isolated). RTS and/or DTR signals should be at the HIGH level to power the device.

K3 (isolated). RTS and/or DTR signals should be at the HIGH level to power the device.

For a PC with 25-way RS232 port:

K422-ISOL (isolated). RTS and/or DTR signals should be at the HIGH level to power the device.

RS232 to RS485 (4-wire) conversion for Master use, externally powered

KD485-STD. Requires +7V to +35V DC power.

RS232 to RS485 (2-wire) conversion, self-powered

For a PC with a 9-way RS232 port:

K2 / K2-ADE (non isolated). DTR should be at the HIGH level to power the device. With K2, RTS controls data direction (the RS232 application must provide RTS Control); with K2-ADE RTS should be permanently HIGH to provide additional power.

K3 / K3-ADE (isolated). DTR should be at the HIGH level to power the device. With K3, RTS controls data direction (the RS232 application must provide RTS Control); with K3-ADE RTS should be permanently HIGH to provide additional power.

For a PC with 25-way RS232 port:

K485-ISOL (isolated). DTR should be at the HIGH level to power the device, and RTS controls data direction (the RS232 application must provide RTS Control).

RS232 to RS485 (2-wire) conversion, externally powered

KD485-STD, requires RTS Control of data direction.

KD485-ADE, has automatic driver enable and does not require RTS control (use Mode 1 built-in program)

Attaching non-addressable RS232 or RS422 devices to an RS485 bus

KD485-ADE, use Mode 2 built-in program. Up to around 30 devices can be multi-dropped on one RS485 (2-wire or 4-wire) bus.

Attaching 2-wire RS485 Slaves to a RS422 (or 4-wire RS485) Master

KD485-ADE-422/422. This is a special-order version with 422/485 interfaces on both sides.

Using a K2-ADE for RS422

The K2-ADE is intended for 2-wire RS485 but it is possible to use it for RS422 (RS422 is an interface where the driver and receiver are permanently enabled).

The key is the note under Fig 5 (the dipswitch diagram) marked (*) in the K2/K2-ADE data sheet which explains the requirements. The requirement for the RTS input to be LOW can be met in one of two ways:

a) Ensure that the application software sets RTS=LOW in the initialisation of the serial port (obviously this is possible only if you can modify the application software), or

b) Construct a simple cable for the RS232 connection between the converter and the PC, containing only the following wires

2-2
3-3
4-4
5-5

This cable ensures that there is no connection to RTS (pin 7).

RS232 Isolation

Important: before ordering, check that the two RS232 devices to be interconnected work together (with a short cable) with just the two data lines (TX,RX) and GND interconnected (i.e. 3 wires total). This ensures that the connection does not require the use of hardware handshakes. This is also true for an RS422-RS422 connection although hardware handshakes are rarely used there.

Inline, Data Transparent:

K3-232 (for DB9 connectors) RTS and/or DTR (preferably both) signals should be at the HIGH level to power the device - this is needed on onse side only; the other side may have just TX,RX,GND connections..

K232-ISOL (for DB25 connection) RTS and/or DTR (preferably both) signals should be at the HIGH level to power the device - this is needed on onse side only; the other side may have just TX,RX,GND connections.

DIN Rail mounted, data transparent:

KD485-STD-232-232 Requires +7V to +35V DC power.

DIN Rail mounted, for baud rate / character format conversion:

KD485-ADE-232-232 Requires +7V to +35V DC power.

Data Transparent, over Fibre

KDF-232-XX-XX Requires +7V to +35V DC power.

RS422 Isolation - DIN Rail mounted

Data Transparent:

KD485-STD-422-422 Requires +7V to +35V DC power.

Data Transparent, over Fibre

KDF-422-XX-XX Requires +7V to +35V DC power.

For baud rate / character format conversion:

KD485-ADE-422-422 Requires +7V to +35V DC power.

RS485 Isolation - DIN Rail mounted

4-wire RS485, with baud rate / character format conversion:

KD485-ADE-422-422 Requires +7V to +35V DC power.

2-wire or 4-wire, over Fibre

KDF-422-XX-XX Requires +7V to +35V DC power

RS232 Line Extension

If you need isolation, please see "Isolation Only" above.

Important: before ordering, check that the two RS232 devices to be interconnected work together (with a short cable) with just the two data lines (TX,RX) and GND interconnected (i.e. 3 wires total). This ensures that the connection does not require the use of hardware handshakes.

If you merely wish to extend an RS232 link without isolation, you can use two RS232-RS422 converters connected back to back. The connections between the converters' RS422 interfaces are:

TXA -> RXA
TXB -> RXB
RXA <- TXA
RXB <- TXB
GND -- GND

Suitable products are the K2, K3, K422-ISOL, KD485-STD. All but the K2 will also provide isolation. The K2 and the KD485-STD will support up to 115200 baud; the others are 38400 baud max.

Applications that require 1 or 2 ports

KD485-PROG Two ports. Can be ordered with a combination of RS232, RS4xx, 20mA interfaces. 115200 baud debug output via a dedicated 3rd output-only port. Programmed in C with an external compiler. MODBUS RTU Slave library available.

Applications that require 3 or 4 ports

PPC / PPC-E Four ports. Each port can be user populated to RS232 or RS4xx. Programmed in Pascal (built-in editor+compiler) or in C (external compiler).