Hello Friends,

I am new to this Embedded Industry,
please help me to solve the problems
I am going to connect three usart Devices ,they are

1.GSM SM 900 A (RS 232)
2.GPS MODEM (RS 232)
3.CREDIT CARD SWIPING MACHINE(RS 232 )

I am using avr MICROCONTOLLER atmega 162.I need to read only one device at the same time

My requirement is I need to read i.e)send to and receive data from these devices through the ATMEGA 162.Do we have any MULTIPLEXER and DEMULTIPLEXER that is workingboth as multiplexer and demultiplexer simultaneously.please help me out please