On 11 May 2009 at 17:12, solarwind wrote:
> ---
> RE: Receiver Output Enable. RO [sends data INTO the PIC] is enabled
> when RE is low; RO is
> high impedance when RE is high.
> 
> DE: Driver Output Enable [sends data OUT from the PIC]. The driver
> outputs, Y and Z, are enabled
> by bringing DE high. They are high impedance when DE is low. If
> the driver outputs are enabled, the parts function as line drivers.
> While they are high impedance, they function as line receivers if
> RE is low.
> ---
> 
> So does this mean that the receiver and the driver should be kept in
> high impedance when I'm not doing anything? If it does, then how do I
> know when I should enable the receiver?

No point in keeping both disabled, enable the receiver when you want to receive, 
enable the transmitter when you want to transmit. As the two enable lines use 
opposite logic it is quite common to tie the two enable lines together so you only 
need one control line from the micro... that way receiver is disabled when 
transmitting, and when transmit is done you go back to listening to the bus. Easiest 
protocols have one master, slaves are not allowed to transmit until they are 
addressed and commanded to by the master.
-- 
Brent Brown, Electronic Design Solutions
16 English Street, St Andrews,
Hamilton 3200, New Zealand
Ph: +64 7 849 0069
Fax: +64 7 849 0071
Cell: +64 27 433 4069
eMail:  brent.brown@clear.net.nz


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