Aside from sleep functions the only impact CAP_EFR makes is enabling
automatic CTS flow control. Below the cite from 16C950 data sheet:
"EFR[7]: Enable automatic CTS flow control.
logic 0 ⇒ CTS flow control is disabled (default).
logic 1 ⇒ CTS flow control is enabled in Enhanced mode
(i.e. EFR[4] = 1), where the data transmission is
prevented whenever the CTS# pin is held
inactive high. 650 and 950-mode drivers should
use this bit to enable CTS flow control. 750
mode drivers should use MCR[5].
When automatic CTS flow control is enabled and the CTS#
input becomes active, the UART will disable transmission
as soon as any current character transmission is complete.
Transmission is resumed whenever the CTS# input
becomes inactive. "
I've tested with such an UART and transmitted some chunk of data with
and without RTS/CTS flow control enabled at 460800 b/s. The test
showed that in enabled state all data was transmitted correctly.
Without RTS/CTS flow control enabled there was massive data loss, as
expected. So the flow control function seems to work correctly.
Regards,
Yegor
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