THVD2450: THVD2450 and SN65HVD72

Hi Murli,

For your first question - based on how you are defining master and slave you need a full duplex device - not a half duplex one. So instead of the THVD2450 you would look at the THVD2442/THVD2452V for higher data speed applications and I generally wouldn't pick a SN65 device above a THVD device so instead of the SN65HVD72 I'd pick something like THVD2412 which is a slower speed grade and if you need 3.3V - if you can swing a 5V supply and don't need the high fault protection on the IC for the slower speed grade the THVD1512 is an option - if you need the 3.3V support maybe look at the THVD1424 which has a slew rate limit which can limit the max speed for EMI considerations. 

Here is a diagram of a 3 node full duplex system 

For your second question - if you only have 1 GPIO the general idea is to either short DE and /RE together with a pull-down - so the GPIO pulls high and the device is in transmit mode and if the GPIO is off or pulls low the device is in /RE mode. Another option is to pull down /RE to gnd - and just always have the receiver on where the DE pin is controlled by the GPIO pin. Basically the receiver being on doesn't affect any devices ability to drive a signal - but the DE pin needs careful consideration. The "master" node of your system can have DE pulled to 3.3V - because the master nodes transmitter is only connected to receiver pins - the draw back here is that if DE is always pulled high you will be burning a lot of power because that means the driver is always active - this can be done but if power usage is a consideration of the design that is one draw back - however on the slave devices DE cannot be pulled up at all times if you have more than 1 slave device - because all the slaves transmitters are tied together since they all loop back to the master nodes receiver input. 

Please let me know if you have any other questions and I will see what I can do!

Best,

Parker Dodson