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Discussion Groups | 68HC12 | can SCI1 and SCI0 be used in diffrent baud rates?
Join our technical discussions about Freescale Microcontrollers: M68HC12. (Freescale Semiconductor is a Subsidiary of Motorola).
can SCI1 and SCI0 be used in diffrent baud rates? - swapna gurumani - Nov 19 16:17:53 2007
I am using both SCI1 and SCI0 in the 68hc12 dragon12 board. MC1 transmits to MC2 on SCI1
at 9600bps. MC2 replies to MC1 on SCI0 using 2400 bauds rate.
I am able to transmit fine on SCI1 from MC1 and MC2. but MC1 is not able to receive the reply from MC2. I have checked using a scope that data is going out of pin ps1of MC2 and the signal does appear on pin ps0 of MC1. based on this reply MC1 should perform specific actions. Why is MC1 not able to understand the signal??
Regards
Swapna
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I am able to transmit fine on SCI1 from MC1 and MC2. but MC1 is not able to receive the reply from MC2. I have checked using a scope that data is going out of pin ps1of MC2 and the signal does appear on pin ps0 of MC1. based on this reply MC1 should perform specific actions. Why is MC1 not able to understand the signal??
Regards
Swapna
---------------------------------
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Re: can SCI1 and SCI0 be used in diffrent baud rates? - Stephen Trier - Nov 20 15:08:52 2007
Swapna,
Yes, SCI0 and SCI1 can certainly be used at different baud rates.
It's hard to say what could be wrong. Here are some general debugging
suggestions:
Double-check your configuration for SCI0, particularly the baud rate
divisor. (You didn't accidentally cut-and-paste the 9600 baud settings,
did you? That's a common variety of mistake to make.) Go through every
bit of every configuration register and make sure they are correct.
Double-check every use of every SCI register in your code and make sure
you aren't accidentally using an SCI1 register when you meant to look at
SCI0, or vice versa. (Again, an easy cut-and-paste mistake to make.)
Write a simple program for MC2 that generates a single character on
demand (not in response to MC1), then write a simple program for MC1
that incorporates your MC1 serial port driver code. In general, try to
simplify your program to the smallest version that still doesn't work.
Usually when one does that, the problem becomes obvious pretty quickly.
Get in there with a debugger (BDM pod) and see what the SCI0 registers
are telling you -- does it have a character buffered? Did it not
register any character at all? Does it indicate a framing error or
other problem? All of those are hints you can use to figure out if the
problem is your register settings or your program logic.
Good luck!
Stephen
(You need to be a member of 68hc12 -- send a blank email to 68hc12-subscribe@yahoogroups.com )
Yes, SCI0 and SCI1 can certainly be used at different baud rates.
It's hard to say what could be wrong. Here are some general debugging
suggestions:
Double-check your configuration for SCI0, particularly the baud rate
divisor. (You didn't accidentally cut-and-paste the 9600 baud settings,
did you? That's a common variety of mistake to make.) Go through every
bit of every configuration register and make sure they are correct.
Double-check every use of every SCI register in your code and make sure
you aren't accidentally using an SCI1 register when you meant to look at
SCI0, or vice versa. (Again, an easy cut-and-paste mistake to make.)
Write a simple program for MC2 that generates a single character on
demand (not in response to MC1), then write a simple program for MC1
that incorporates your MC1 serial port driver code. In general, try to
simplify your program to the smallest version that still doesn't work.
Usually when one does that, the problem becomes obvious pretty quickly.
Get in there with a debugger (BDM pod) and see what the SCI0 registers
are telling you -- does it have a character buffered? Did it not
register any character at all? Does it indicate a framing error or
other problem? All of those are hints you can use to figure out if the
problem is your register settings or your program logic.
Good luck!
Stephen
(You need to be a member of 68hc12 -- send a blank email to 68hc12-subscribe@yahoogroups.com )