need help-max487 based multiple transmitter & single receiver networking

[tapasparua]

i am trying to design a microcontroller based fault detection system where a single receiver will receive any data from multiple transmitters. it is assumed that at a time only one transmitter will send the data. all microcontrollers belong to 8051 family, and have a 11.059MHz crystal. the baud rate is 9600bps. i have used max487 for the networking. now when a single transmitter is attached to the network, the receiver works. but when i add another transmitter (tot 2 transmitters & 1 receiver in the network), the receiver does not respond. i checked with logic probe that no data is reaching at rx pin of receiver. the number of transmitter will be upto 127. please suggest.

 

[Golden Electronics]

1. How ensure that both transmitter not sensing data at time. If this thing happen then data collision occur.
2. For such multi device u need Modbus protocol for communication. Because if ur receiver never identify who sending what data.
3. U required to sense bus is busy. if use Master Slave concept then each time master send request to slave 1...slave 128 status. For each
slave response if it match it's ID & then respond wit data.
4. For this ur Enable signal require to be controlled according to Tx-Rx data condition