Rohde & Schwarz 1094.0006.50, Operating Manual

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CTS55 Interfaces/Annex A
1094.0006.55 A.3 E-3
Handshake
Software handshake
In the case of the software handshake, the data transfer is controlled using the two control characters
XON / XOFF.
The CTS uses the control character XON to indicate that it is ready to receive data.
If the receive buffer is full, it sends the XOFF character via the interface to the controller. The controller
then interrupts the data output until it receives another XON from the CTS.
The controller indicates to the CTS that it is ready to receive data in the same way.
Cable for local controller coupling in the case of software handshake
The connection of the CTS with a controller in the case of software handshake is effected by crossing
the data lines. The following wiring diagram applies to a controller with 9-pin or 25-pin configuration.
CTS Controller CTS Controller
9-pin 9-pin 9-pin 25-pin
1
2
3
4
5
6
7
8
9
------------RxD / TxD---------------
------------TxD / RxD---------------
------------GND / GND-------------
1
3
2
6
5
4
8
7
9 1
2
3
4
5
6
7
8
9
------------RxD / TxD---------------
------------TxD / RxD---------------
------------GND / GND-------------
8
2
3
6
7
20
5
4
22
Fig. A3-2 Wiring of the data lines for software handshake
Hardware handshake
In the case of the hardware handshake, the CTS indicates that it is ready to receive data via the lines
DTR and RTS. A logic ’0’ on both lines means "ready" and a logic ’1’ means "not ready". The RTS line is
always active (logic ’0’) as long as the serial interface is switched on. The DTR line thus controls the
readiness of the CTS to receive data.
The readiness of the remote station to receive data is reported to the CTS via the CTS and DSR line. A
logic ’0’ on both lines activates the data output and a logic ’1’ on both lines stops the data output of the
CTS. The data output is effected via the TxD line.