Henrik Karlsson

Waking up from LPRun/LPWait - MC9S08QE64

Discussion created by Henrik Karlsson on Feb 1, 2008
Latest reply on Feb 4, 2008 by Jim Donelson
Hi folks,

I have a queation for you guys.
I have a system that's supposed to run on a S08QE64. In one of the modes it only communicates on a UART. Since it is a battery driven system I want to save as much power as possible.
What I want to do is wake up from some LP mode whenever data is recieved on the uart, process the data, and then go back to sleep again. I have no control over the data sent to me, and it has to be in 57,6 kbaud.
My first question: Is this possible without losing the first bit (at the given baud rate)?
My second question: Other modes of the application requires some computaional power, so running at a low clock all the time is out of the question (I would prefer an external high freq. crystal), and LPWait and LPRun seem to demand external clock, but there is only one clock input to the mcu? So if i want to use the LP modes, i have to use the internal osc. in run mode and an exernal low freq. source in LP?

Im new to this chip, hence all the stupid questions. :smileyhappy:

Best regards

Message Edited by NLFSJ on 2008-02-02 07:56 AM



Added p/n to subject.

Message Edited by NLFSJ on 2008-02-02 07:56 AM