Answer: When AT&K3 is set to enable the hardware flow control
If you toggle RTS to inactive, the terminal will be not able to receive the data from the module any more. As a result, the data is buffered…
If you toggle RTS back to active, the buffered data will be sent to PC immediately.
When AT&K0/AT&K4 is set to disable hardware flow control:
If you toggle RTS to inactive or active, then no impact for the data, the terminal will still be able to receive the data from the module.