timers in Software UART..

IF TWO SOftware uart is implemented in the arduino programming for arduino uno.. which are the timers will be utilized for generating those UART signals?

and if the Software UARTs are using dedicated timers for the signal generation. in Arduino Uno we can't use more the three software UARTs ah?

see this page

and read this too about newsoftserial (which is now the default)

If using multiple software serial ports, only one can receive data at a time.
....

If your project requires simultaneous data flows, see Paul Stoffregen's AltSoftSerial library. AltSoftSerial overcomes a number of other issues with the core SoftwareSerial, but has it's own limitations. Refer to the AltSoftSerial site for more information

or the Two Port Receive example

IF TWO SOftware uart is implemented in the arduino programming for arduino uno.. which are the timers will be utilized for generating those UART signals?

Only one timer is used, regardless of how many instances of the class there are.

and if the Software UARTs are using dedicated timers for the signal generation. in Arduino Uno we can't use more the three software UARTs ah?

The instances do not use separate timers.

Is there any restriction for number software UARTs i can create???

Prithiviraj_pandian:
Is there any restriction for number software UARTs i can create???

Yes, the number of pins available with change interrupts.

The library has the following known limitations:
If using multiple software serial ports, only one can receive data at a time.
Not all pins on the Mega and Mega 2560 support change interrupts, so only the following can be used for RX: 10, 11, 12, 13, 14, 15, 50, 51, 52, 53, A8 (62), A9 (63), A10 (64), A11 (65), A12 (66), A13 (67), A14 (68), A15 (69).
Not all pins on the Leonardo and Micro support change interrupts, so only the following can be used for RX: 8, 9, 10, 11, 14 (MISO), 15 (SCK), 16 (MOSI).
On Arduino or Genuino 101 the current maximum RX speed is 57600bps
On Arduino or Genuino 101 RX doesn't work on Pin 13

NeoSWSerial does not use any timers, but it is limited to baud rates 9600, 19200 and 38400. It can transmit and receive at the same time. It's also much more efficient because it does not disable interrupts for the entire duration of a received character. Like other software serials, you can only listen (receive) from one pin at a time.

AltSoftSerial is even better, but it only works on two specific pins (8 & 9 on an UNO), it prevents the use of PWM on pin 10, and it uses TIMER1. Strongly recommended.

Cheers,
/dev

And the "only one receive at a time" is usually a major limitation, indicating you need to switch to a 'bigger' Arduino. The new Teensy 3.6 has 6 hardware UARTs.

Often a Micro is enough, since the USB serial is separate to the hardware serial and then you can add one SoftwareSerial. (Although the pins on the Micro are even more restricted for SoftwareSerial.)