Jackie Chan wrote:
> I have a project like this. A master modem and many slave modems.
> Master modem will send an id and matched slave id modem will return
> some data. The baud rate is fixed at 1200. I am planning to use
> Rockwell or Zilog single chip modem ICs. And i am going to use 4 wire
> phone system. The tx of master will be connected to rx of all slave
> modems. And if the id is matched tx of the slave will be connected to
> master. Only the master can initiate the communication.
> The problem is this - Without handshaking is it possible to send data
> through modem? Handshaking is not possiable because there are many
> slave modem.
Handshaking is not necessary, especially when your protocol is good.
> The id is unique for every modem. But i can't initiate dialing some
> number and contact the slave. The id will be placed on the bus by
> master modem and slave will recognise its id and return some data.
> (id matching is done by 89c55
Just make sure that you have a timeout on the message standing open.
If you only want to communicate with only one slave at a time, this is
very well possible. This looks like a typical network. How far are you
going? You can go many kilometers with RS485 at 1200 Bd.
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