16 bit transfer with rs232

[krakatau]

hi,
My question is very short.
I want to 16bit transfer with rs232 protocol, is it possible?
What do I do?
I will use to pic16f876 to 16bit shift register.
16bit transfer or 8bit 8bit transfer.

thanks

[Guest]

Hi krakatau, you have to send 8 bits and then another 8 bits. If you want to recieve it in a 16 bits register you have to do something like this:

var=BufferReception;
var=(var<<8)| BufferReception;

your 'var' has the 16bits data you wanted to send. But you have to be careful with the first 8 bits that you send, in this example I send the upper 8bits and then the lower.

[Ttelmah]

Remember also, that with RS232, there are start and stop bits each side of the data. To transfer directly to a shift register, you'd really want to be using SSP, then a clock is provided as well, and if you implement slave select, this can reset the shift register. Again 8 bit transfers, but you simply operate the select line, and send two transfers, which will include the clocks to operate the register.

Best Wishes

[krakatau]

first of all thanks your quickly replies.. i suppose rs232 can't 16bit transfer directly.it s true? i worked that ;
16bit data, from PC to pic16f876 to another pic16f876 and then this 16bit data will send to 16bit shift register. so 16f876-16f876-shiftregister-on the shiftregister_output.
yesterday i wrote like above code;
for master;

[krakatau]

have you any idea??

[Ttelmah]

You have already had a full reply. Look at the first line, of the very first reply, for what you are missing.

Best Wishes

[SherpaDoug]

RS232 or any other serial transfer can't send 16 bits at a time. It cant even send 8 bits at a time. Serial transfers send ONE bit at a time. The usual PIC or PC hardware UART does a serial to 8 bit parallel conversion, but a custom software UART could operate with any word width desired.

Look up the CCS functions make8() and make16().
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[krakatau]

I found my code is wrong because putc() function's back value have to be 8bit. Its a CCS rule. I tried 16bit transfer. I'll send 8bit, 8bit data transfer, I'm forced to.
I'm ok. Thanks a lot.

[Ttelmah]

Not a 'CCS Rule'. A rule if you are talking to an interface supporting byte transfers. Same happens in C on the PC, if you are talking to the RS232...

Best Wishes

[dyeatman]

The UART hardware parallel to serial shift register only supports 8 bits as well.... It has NOTHING to do with CCS.