Raveon RV-M7 Spécifications télécharger pdf (Page 61)

RV-M7 Technical Manual

15.4 Null modem with full handshaking

Caution: Most null modem cables are designed for host-to-host communication and will not work

for device-to-device communication! See the section on compatibility issues for more details.

In this null modem cable, seven wires are present. The cable is shown in the following figure.

Null modem with full handshaking

(DB-9 Female shown. Same wiring for male-to-male cable)

Connector 1

Connector 2

Function

DTR

DSR

Signal ground

DSR

DTR

RTS

CTS

RTS

15.5 Compatibility issues

The null modem cable with full handshaking does not permit the older way of flow control to take

place. The main incompatibility is the cross connection of the RTS and CTS pins. Originally, these

pins are used for a question/answer type of flow control. When the full handshaking null modem

cable is used, there is no request anymore. The lines are purely used for telling the other side if

communication is possible.

The main advantage of this cable is, that there are two signaling lines in each direction. Both the

RTS and DTR outputs can be used to send flow control information to the other device. This

makes it possible to achieve high communication speeds with this type of null modem cable,

provided that the system has been designed for it.

Off-the-shelf Host-Host Null Modem Cables

Many off-the-shelf host-to-host null modem cables will not work with the M7 (or any serial device).

These cables will wire pins 1 and 6 together, which will connect two outputs together and cause

unpredictable issues. If buying off-the-shelf cables, it is important to look for cables that are

designed for device-to-device communication (generally with male connectors on either end) and to

verify that no shorting connections are made within the cable.

1 2 ... 56 57 58 59 60 61 62 63 64 65 66 67

Pas de commentaire

Raveon RV-M7 Spécifications Page 61