#use RS232 with enable for RS485, what is the problem???

[doenza]

When I use enable pin with #use RS232 for transmit data,I can transmit data;

#use RS232 (baud=9600, xmit=pin_C6, rcv=pin_C7,enable=pin_C5,parity=N,bits=8, STREAM=RS485)

but I can not receive data
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Then When I dont use enable pin with #use RS232 for transmit data,I can not transmit data;

#use RS232 (baud=9600, xmit=pin_C6, rcv=pin_C7,enable=pin_C5,parity=N,bits=8, STREAM=RS485)

but I can receive data

Is there any one knows reason or what can I do;

[Ttelmah]

Your wiring to the 485 buffer is wrong.
The 'enable' line, wants to go to the _transmit enable_ pin of the 485 driver, _not_ the main chip 'enable'. If you connect it to the latter, the whole chip is turned off, and can't receive.
If you want to operate the chip enable (to save power), you need to do this with a separate line, and turn the chip off when you don't want to send/receive anything.

Best Wishes