RTS/CTS Handshake, Jumpers J10-12 | Quatech RS-485 manual

7 External Connections

The DSC-200/300 provides four differential communication signals per channel. The two output signals are Transmit Data (TxD) and Auxiliary Output (AUXOUT). The two input signals are Receive Data (RxD) and Auxiliary Input (AUXIN). A ground signal is also provided.

The available input signals for AUXIN are Clear To Send (CTS) and the Receive Clock (RCLK). The available output signals for AUXOUT are Request To Send (RTS), the Transmit Clock (TCLK), and the AUXIN signal (for loopback). Either half-duplex or full-duplex operation can be selected for each communications channel. Auto-Toggle is also jumper selectable .If half-duplex operation is selected, one of the UART's signals (either DTR or RTS) is used to enable the transmitter drivers. The inverse of the transmitter enable can be used to enable the receiver drivers.

Configuration is done using jumpers J10 through J23 for interface signal routing. Each jumper block provides the same functions for its particular channel. All below examples are for Channel 1. Channel 2 is the same but different sets of jumpers. See Figure 15 for Channel 2 jumpers.

Channel	Signal routing
Port 1	J10-16

Port 2	J17-23

Figure 15 --- Jumper/Channel correspondence

7.1 RTS/CTS Handshake

Transmission of RTS, combined with reception of CTS, allows for hardware handshaking (data flow control) between the UART and the external device. RTS is transmitted on AUXOUT by not connecting pins 1 and 2 of the jumper blocks J11-12. CTS is received on AUXIN by not connecting pins 1 and 2 of the jumper block J10. If RTS/CTS handshaking is not desired, the RTS output can be looped back to the CTS input by connecting pins 1 and 2 of the jumper block J10. Figure 16 shows how to select the RTS/CTS mode.