efficient method to create a clock signal with a general purpose IO

Doug McKenney

Other Parts Discussed in Thread: MSP430F5438

We are generating a clock for our system by toggling a general purpose IO. We'd like to increase the frequency of this clock as much as possible. Is there a way to route any of the input clocks to an output? If not, do you have any suggestions about the most efficient method to generate this clock in the code?

thanks!

over 14 years ago

0 eltury over 14 years ago

Genius 3330 points

You can route internal clocks to output pins. What chip?

0 Jason Kriek over 14 years ago

TI__Expert 5210 points

Doug,

The MCLK,SCLK, and ACLK can be routed out to specefic pins. Go to the landing page for the device that you are using at www.ti.com , and look for the code source examples.

Open the readme.txt file, and read through the examples. One of the examples will show how to output these clocks to a pin.

In the future it would be benifical to indicate which device and which compiler you are using.

-Jason

0 Doug McKenney over 14 years ago in reply to eltury

Prodigy 90 points

MSP430F5438 and Code Composer Studio tools. Thanks Jason!

0 Jason Kriek over 14 years ago in reply to Doug McKenney

TI__Expert 5210 points

Doug,

1. Go here: http://focus.ti.com/docs/prod/folders/print/msp430f5438a.html

2. Search for "examples".

3. Download the zip file.

4. Look at readme.txt file.

5. See example for msp430x54xA_UCS_1.c

This will output the clocks to the pins. You can set dividers to get the clock frequence that you want.

-Jason

0 Doug McKenney over 14 years ago in reply to Jason Kriek

Prodigy 90 points

Thanks for the detailed help, Jason! I found what I needed with your first response

0 Jens-Michael Gross over 14 years ago in reply to Doug McKenney

Guru 227245 points

Doug McKenney said:
MSP430F5438

the 5438 has an optional divider that allows outputting 1/2 or 1/4 of ACLK to the dedicated output pin.

Also, you can use the timer CCR units to output any frequency that is at least (A/SM)CLK/2 to their output pins.

But for highest frequency, the direct ACLK/MCLK/SMCLK output pins are best. Note that SMCLK/ACLK can be higher than MCLK, so you don't need to run the CPU on the same (high) frequency as the clocks.

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efficient method to create a clock signal with a general purpose IO