RS485

RS485 is available with the following configuration:

USART frame format (CTRLA.FORM = 0x00 or 0x01)
RS485 pinout (CTRLA.TXPO=0x3).

The RS485 feature enables control of an external line driver as shown in the figure below. While operating in RS485 mode, the transmit enable pin (TE) is driven high when the transmitter is active.

Figure 1. RS485 Bus Connection

The TE pin will remain high for the complete frame including stop bit(s). If a Guard Time is programmed in the Control C register (CTRLC.GTIME), the line will remain driven after the last character completion. The following figure shows a transfer with one stop bit and CTRLC.GTIME=3.

Figure 2. Example of TE Drive with Guard Time

The Transmit Complete interrupt flag (INTFLAG.TXC) will be raised after the guard time is complete and TE goes low.