Datasheet

711
SAM9261 [DATASHEET]
Atmel-6062O-ATARM-SAM9261-Datasheet_21-Jun-16
42.1.18 USART
42.1.18.1 USART: CTS signal in Hardware Handshake
When Hardware Handshaking is used and if CTS goes low near the end of the starting bit of the transmitter, a
character is lost.
Problem Fix/Workaround
CTS must not go low during a time slot comprised between 2 Master Clock periods before the rising edge of the
starting bit and 16 Master Clock periods after the rising edge of the starting bit.
42.1.18.2 USART: RTS unexpected behavior
1. Setting the receiver to hardware handshaking mode drops RTS line to low level even if the receiver is still
turned off. USART needs to be completely configured and started before setting the receiver to hardware
handshaking mode.
2. Disabling the receiver during a PDC transfer while RXBUFF flag is '0' has no effect on RTS. The only way to
get the RTS line rising to high level is to reset both PDMA buffers by writing the value ‘0’ in both counter
registers.
Problem Fix/Workaround
None.
42.1.18.3 USART: TXD signal is Floating in Modem and Hardware Handshaking Mode
TXD signal should be pulled up in Modem and Hardware Handshaking mode.
Problem Fix/Workaround
TXD is multiplexed with a PIO which integrates a pull-up resistor. This internal pullup needs to be enabled.
42.1.18.4 USART: DCD is Active High Instead of Low
DCD signal is active at “High” level in USART block (Modem Mode).
DCD should be active at “Low” level.
Problem Fix/Workaround
Add an inverter.