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Discussion Groups | 68HC12 | hc912D60 clock 1/2 Xtal?
Join our technical discussions about Freescale Microcontrollers: M68HC12. (Freescale Semiconductor is a Subsidiary of Motorola).
hc912D60 clock 1/2 Xtal? - Wade A Smith - Dec 19 8:46:00 2003
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I was sent to this group by Technological Arts support page. I purchaced one of their Adapt912DT60 boards. I was following JWValvano's examples from his book "Intro to Embedded Microcomputer Systems" and ran into problems. He uses 52 to generate 9600 BAUD for 8MHz HC12. I couldnt get anything other than garbage. I wrote a program to vary the value that I put into SC0BD and then watch on the RS232 terminal to see a good response. BTW, my delay between messages was twice as long as it should have been. I got clear messages when the value became 25, 25 and 27. I conclude that I'm running the 68HC912D60 at 4MHz with an 8MHz crystal. How do I crank up the PLL and get it running at 8MHz? It's supposed to be able to run that fast, so how do I get it there? wade in Flour-dough |
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Re: hc912D60 clock 1/2 Xtal? - Doron Fael - Dec 21 3:29:00 2003
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Hello Wade, First of all you need to have VDDPLL connected to 5V, to allow the PLL to be engaged. You also need a network of two capacitors and a resistor to be connected to the XFC pin. The value of the capacitors and resistor matter. Then in your code you need to write the SYNR and the REFDV registers. For a multiply by 2 you can program both SYNR and REFDV to 0. Then wait until the LOCK bit in the PLLFLG register becomes set (the PLL has locked on the new frequency). Then finally set the BCSP bit in the CLKSEL register - to use the PLL frequency as the clock source. Hope this helps, Doron Nohau Corporation HC12 In-Circuit Emulators www.nohau.com/emul12pc.html At 08:46 19/12/2003 -0500, you wrote: >I was sent to this group by Technological Arts support page. >I purchaced one of their Adapt912DT60 boards. > >I was following JWValvano's examples from his book >"Intro to Embedded Microcomputer Systems" and ran into >problems. He uses 52 to generate 9600 BAUD for 8MHz HC12. >I couldnt get anything other than garbage. I wrote a program >to vary the value that I put into SC0BD and then watch on >the RS232 terminal to see a good response. BTW, my delay >between messages was twice as long as it should have been. >I got clear messages when the value became 25, 25 and 27. > >I conclude that I'm running the 68HC912D60 at 4MHz with an 8MHz crystal. > >How do I crank up the PLL and get it running at 8MHz? >It's supposed to be able to run that fast, so how do I get it >there? > >wade in Flour-dough [Non-text portions of this message have been removed] |
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Re: hc912D60 clock 1/2 Xtal? - Wade A Smith - Dec 23 8:17:00 2003
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On 22 Dec 2003 08:09:49 -0000 writes: > Date: Sun, 21 Dec 2003 10:29:00 +0200 > From: Doron Fael <> > Subject: Re: hc912D60 clock 1/2 Xtal? > > Hello Wade, > > First of all you need to have VDDPLL connected to 5V, to allow the > PLL to > be engaged. You also need a network of two capacitors and a resistor > to be > connected to the XFC pin. The value of the capacitors and resistor > matter. > > Then in your code you need to write the SYNR and the REFDV > registers. For a > multiply by 2 you can program both SYNR and REFDV to 0. Then wait > until the > LOCK bit in the PLLFLG register becomes set (the PLL has locked on > the new > frequency). Then finally set the BCSP bit in the CLKSEL register - > to use > the PLL frequency as the clock source. > > Hope this helps, Yes, it helps. I was poking around in the TechArts boot code and it looks like they do something similar, but they are setting it slower. The problem seems to be that they get to it at boot up time, long before I come along and they set it sloooowww. I wonder if they supply the source code for users to tweak it to what they want -- it is such a pain using the BDM to find out how the wheel has already been invented... > Doron > Nohau Corporation > HC12 In-Circuit Emulators > www.nohau.com/emul12pc.html > > At 08:46 19/12/2003 -0500, you wrote: > >I was sent to this group by Technological Arts support page. > >I purchaced one of their Adapt912DT60 boards. > > > >I was following JWValvano's examples from his book > >"Intro to Embedded Microcomputer Systems" and ran into > >problems. He uses 52 to generate 9600 BAUD for 8MHz HC12. > >I couldnt get anything other than garbage. I wrote a program > >to vary the value that I put into SC0BD and then watch on > >the RS232 terminal to see a good response. BTW, my delay > >between messages was twice as long as it should have been. > >I got clear messages when the value became 25, 25 and 27. > > > >I conclude that I'm running the 68HC912D60 at 4MHz with an 8MHz > crystal. > > > >How do I crank up the PLL and get it running at 8MHz? > >It's supposed to be able to run that fast, so how do I get it > >there? > > > >wade in Flour-dough |
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