Hi,
I am trying to realise a RS485 in 4 wire mode which I feel is nothing but RS-422 in balanced full duplex mode.
This is to support physical layer of a Industrial protocol on my board
On this board, The Tx_EN is controlled by a CPLD and its address is available to me . The Rx_EN is pulled to ground via a resistor.
These are the only details available from board's side.
Now i have some questions regarding the implementation of low level driver for my RS-422.
1. Since 422 is full duplex, is there any explicit need to enable the TX_EN pin memory mapped on CPLD ( Scenario : disabling Rx before to send as in 485 and so on..) - basically any special handling of the Tx/Rx EN pins
2. Requirement is that we need a point to point Rs422 link between 2 devices ( both of them very near to each other)in this case is the Termination resistor requirred? ( Our board has a switch for modes -with /without termination) .
3. Any special handling required in Sw for the driver ( If both devices attempt to Tx or Rx to each other)
4. On Rx side, the data is received sometimes as just 2 bytes and sometimes upto 255 bytes , how to handle this feature?
5. Example of 422 driver ( links, app.notes etc..)
Thanks in advance ,
Prasad
