Quatech RS-485 user manual AUXIN/AUXOUT Loopback, AUXIN/AUXOUT loopback

7.4 AUXIN/AUXOUT Loopback

The AUXIN signal is an input from the external device, and connecting it to the AUXOUT signal provides for a loopback mode of operation. In other words, whatever signal is transmitted by the external device over the AUXIN line will be fed back to the external device over the AUXOUT line. This mode is accomplished by connecting pins 1 and 2 of the jumper blocks J11 and J12. Figure 19 shows how to select this loopback mode.

Jumpers J11-13

J11

J12

J13

AUX0_SEL0 AUX0_SEL1

RCLK0_SEL

Loopback AUXOUT to AUXIN

Figure 19 --- AUXIN/AUXOUT loopback

7.5 Half-Duplex/Full-Duplex/Auto-Toggle Selection

Using jumper blocks J14 thru J16, the transmitters and receivers of each channel can be enabled and disabled by modem control signals. This allows operation in both half-duplex, full-duplex or Auto-Toggle modes.

The transmit drivers can be controlled by either the Data Terminal Ready (DTR) or the Request to Send (RTS) output from the UART. If a jumper is applied between pins 1 and 2 of jumper block J14, the drivers are enabled for TxD and AUXOUT when the UART's DTR signal is asserted. If a jumper is applied between pins 1 and 2 of jumper block J15, the drivers are enabled for TxD and AUXOUT when the UART's RTS signal is asserted. If neither of these jumpers is applied, the drivers remain enabled at all times. When disabled, the transmit drivers enter a high-impedance state.

The receivers can be controlled by the inverse of the transmit enable. If a jumper is applied between pins 1 and 2 of jumper block J16, the receivers for RxD and AUXIN will be disabled when the transmit drivers are enabled and vice-versa (based on the DTR or RTS connections on pins 1-2 of J14 and J15.

To operate in half-duplex DTR mode, apply jumpers between pins 1 and 2 of jumper blocks J14 and J16. To operate in half-duplex RTS mode, apply jumpers between pins 1 and 2

.of jumper blocks J15 and J16

To operate in full-duplex mode, leave the jumpers in their factory default locations, installed in the spare locations of J14-16 only. The drivers and receivers are always enabled in full-duplex mode. For Auto-Toggle, apply jumpers between pins 1 and 2 of jumper blocks J14 and J15. Figure 20 shows how to select half-, full-duplex or Auto-Toggle operation.

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