D-Link DE-805TP - 10Mbps Ethernet Mini Hub User Manual download pdf (Page 31)

Modbus for Field Technicians

Page 31

15. MODBUS ON RS232

RS232 requires a minimum of 3 conductors to connect the two devices. Rx, Tx

and Ground.

Some devices implement hardware handshaking. This means that before they

send a message some voltage must be applied to one of the other pins on the

port. If hardware handshaking is active on the device, then you will never get

a response until you bypass it or implement it. We recommend bypassing it

because there are often differences in the ways that vendors implemented it.

Here are typical jumper schemes that can be applied to defeat handshaking.

Connect these pins together on the 9 Pin D-Type connector connected to the

server device.

Pin Function

‘1 DCD

4 DTR

6 DSR

And

Pin Function

‘7 RTS

‘8 CTS

‘9 RI (often omitted)

1 2 ... 26 27 28 29 30 31 32 33 34 35 36 ... 76 77

No comments

D-Link DE-805TP - 10Mbps Ethernet Mini Hub User Manual Page 31