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how make 2 source to connect PIC18F452 with rs232 ?

 
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how make 2 source to connect PIC18F452 with rs232 ?
PostPosted: Thu Oct 12, 2006 9:45 am     Reply with quote
help me!!
asmallri



Joined: 12 Aug 2004
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PostPosted: Thu Oct 12, 2006 10:13 am     Reply with quote
Use the hardware UART for the high speed port and a software UART for the low speed port.
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SherpaDoug



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PostPosted: Thu Oct 12, 2006 5:48 pm     Reply with quote
If the two sources are never active at the same time you can use a NAND gate to combine them into one UART. Put the NAND gate on the TTL line
between the RS232 level shifter and the PIC.

If you do use the hardware UART for the high speed port and a software UART for the low speed port then the processor will be busy the whole time the low speed port is recieving. That may cause the hardware UART buffer to overflow. If you reverse them the CPU won't be busy for so long.
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asmallri



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PostPosted: Thu Oct 12, 2006 7:09 pm     Reply with quote
Code:
If you reverse them the CPU won't be busy for so long.


It depends. This is a limitation of the CCS software UART implementation not of software UARTS in general.
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