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.