rs232_errors+BIT6

[simon630]

dear gurus,
referring to page 45 of PCB,PCM, and PCW PICC Compiler reference manual, when Bit 6 of rs232_errors variable is set to one, it indicates a put failed in float high mode. could anybody explain what happen and how to resolve? thx in advance.
___________________________
This message was ported from CCS's old forum
Original Post ID: 12484

[PCM programmer]

:=dear gurus,
:=referring to page 45 of PCB,PCM, and PCW PICC Compiler reference manual, when Bit 6 of rs232_errors variable is set to one, it indicates a put failed in float high mode. could anybody explain what happen and how to resolve? thx in advance.
-----------------------------------------------------

That directive is an option for the #use rs232 statement.
It's only used in two CCS example files: ex_pbusm.c and ex_pbusr.c

Those examples show how to make a small one-wire "network"
between two or more PICs. There is a schematic in the
manual, and in the FAQ which shows the connections:
<a href="http://www.ccsinfo.com/faq/?23" TARGET="_blank">http://www.ccsinfo.com/faq/?23</a>
It consists of one wire between Pin B0 on several PICs and
one pull-up resistor. (Of course, there is also a Ground wire).

So a high level is created by the pull-up resistor. The PICs
do not drive pin B0 high. When they want to put out a high
level, they make pin B0 into an input (with the TRIS_B
register), and let the pull-up resistor pull the logic level
up to a high level. CCS calls this "float high". It just
means letting the pull-up resistor take the signal high,
rather than having the PIC drive it high.
___________________________
This message was ported from CCS's old forum
Original Post ID: 12500

[Sherpa Doug]

:=:=dear gurus,
:=:=referring to page 45 of PCB,PCM, and PCW PICC Compiler reference manual, when Bit 6 of rs232_errors variable is set to one, it indicates a put failed in float high mode. could anybody explain what happen and how to resolve? thx in advance.
:=-----------------------------------------------------
:=
:=That directive is an option for the #use rs232 statement.
:=It's only used in two CCS example files: ex_pbusm.c and ex_pbusr.c
:=
:=Those examples show how to make a small one-wire "network"
:=between two or more PICs. There is a schematic in the
:=manual, and in the FAQ which shows the connections:
:= <a href="http://www.ccsinfo.com/faq/?23" TARGET="_blank"> <a href="http://www.ccsinfo.com/faq/?23" TARGET="_blank">http://www.ccsinfo.com/faq/?23</a></a>
:=It consists of one wire between Pin B0 on several PICs and
:=one pull-up resistor. (Of course, there is also a Ground wire).
:=
:=So a high level is created by the pull-up resistor. The PICs
:=do not drive pin B0 high. When they want to put out a high
:=level, they make pin B0 into an input (with the TRIS_B
:=register), and let the pull-up resistor pull the logic level
:=up to a high level. CCS calls this "float high". It just
:=means letting the pull-up resistor take the signal high,
:=rather than having the PIC drive it high.

So if one accidentally got into "float high" mode, and did not have the pull-up resistor, you would get this error, because the non-existant resistor failed to pull the line high when no one else was pulling the line low.

If you have this problem I suggest you look at your #use RS232 statement and find out how you got into "float high" mode.

___________________________
This message was ported from CCS's old forum
Original Post ID: 12503