7.3 XCLK
This is the output clock signal used by the transmitter portion of the UART. It is generally connected to the UART's own receive clock input (RCLK). This is done by connecting pins 3 and 6 of the jumper block. If desired, XCLK can be transmitted to an external source over the AUXOUT line by connecting pins 5 and 6 of the jumper block. Figure 21 shows how to select the XCLK mode.
Jumpers J5, J7
XCLK | 6 | 3 | RCLK | XCLK 6 | 3 | RCLK |
AUXOUT | 5 | 2 | AUXIN | AUXOUT 5 | 2 | AUXIN |
RTS | 4 | 1 | CTS | RTS 4 | 1 | CTS |
Loopback XCLK to RCLK | Transmit XCLK on AUXOUT | |||||
Figure 21 --- XCLK selection
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 2 and 5 of the jumper block. Figure 22 shows how to select this loopback mode.
Jumpers J5, J7
XCLK 6 
AUXOUT 5
RTS 4
3RCLK
2AUXIN
1CTS
Loopback AUXOUT to AUXIN
Figure 22 --- AUXIN/AUXOUT loopback
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