hello..
I am doing a serial communication and doing a loopback test through a PIC 
most of the times the last two or four bytes of a message is not being sent 
back to the sending computer from the PIC...

the computer pulls down a pin to 0volts to tell the PIC that a transmission 
is over and up to tell the PIC that its about to initiate a transmission.. 
The PIC signal a clear to send message by raising another pin to 5 volts...

when the PIC has sent a reply it pulls down this other pin to low and 
disables Transmit Interrupt...

the problem I think is the timing when raising and lowering the said pins. 
when the pins are lowered while some data is still in the PIC's hardware 
buffer.. Some of the last 4 bytes are being lost.. maybe 2 when received and 
2 when transmitting.. I got an idea of checking TXSTA register's TRMT bit to 
check whether the shift register is empty or not before sending a "message 
sent" signal to the computer and disabling interrupt so as not to loose the 
last data sitting on the transmit buffer..

on the other hand.. Is there a way to check the PIC's Receiving Shift 
register if it has data or currently shifting data.. I would like to avoid 
waiting or delay code if it can be avoided...

thanks.. 



-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist