MSP430G2553: MSP430G2553 Clock Speed

Prodigy 60 points

Abu Bakar

Replies: 6

Views: 3643

Part Number: MSP430G2553

Hi all:

I am having trouble figuring out this problem. Maybe someone here can give me some ideas. I am using the TI MSP430 Launchpad. 

I have fixed  the MSP430G2553 clock speed at 8 MHz in the code, and according to the datasheet, the clock speed should increase with increasing voltage. However, when I measure it using DCO calibration technique, I get a decreasing clock speed with increasing voltage. The variation is not too much; it varies between 7.92 to 8.16MHz. But shouldn't it be fixed at 8MHz, or maybe increase? I see nothing in the datasheet that explains this anomaly. 

Any ideas?

• msp430g2553
• clock speed
• DCO
• Oscillator

Prodigy 60 points

Abu Bakar

• May 30, 2017 9:44 AM
• Locked
• Cancel

6 Replies

• Guru 73650 points

  

  Clemens Ladisch

  

  • May 30, 2017 1:01 PM

  Where does the datasheet say that higher voltage results in higher DCO frequency?

  • Locked
  • Cancel

  Do you have another question?

  We are glad that we were able to resolve this issue, and will now proceed to close this thread.

  If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.

  Ask a related question Ask a new question
• Prodigy 60 points

  

  Abu Bakar

  

  • Jun 2, 2017 6:29 PM

  In reply to Clemens Ladisch:

  

  • Locked
  • Cancel

  Do you have another question?

  We are glad that we were able to resolve this issue, and will now proceed to close this thread.

  If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.

  Ask a related question Ask a new question
• Guru 73650 points

  

  Clemens Ladisch

  

  • Jun 2, 2017 6:37 PM

  In reply to Abu Bakar:

  This figure shows allowed frequencies. For example, when V_CC is 2.7 V, then you must not use any frequency higher than 12 MHz.

  • Locked
  • Cancel

  Do you have another question?

  We are glad that we were able to resolve this issue, and will now proceed to close this thread.

  If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.

  Ask a related question Ask a new question
• Prodigy 60 points

  

  Abu Bakar

  

  • Jun 2, 2017 6:56 PM

  In reply to Clemens Ladisch:

  Thanks Clemens.
  Can you please answer the other half of my question i.e., why is the clock speed decreasing with increase in voltage? I am using following code to set the DCO frequency to 8MHz
  
  BCSCTL1 = CALBC1_8MHZ;
  DCOCTL = CALDCO_8MHZ;
  
  I am getting these frequency values
  
  Voltage(V) Clock Speed(MHz)
  2.3 8.2
  2.5 8.1
  3.0 8.0
  3.5 7.9

  • Locked
  • Cancel

  Do you have another question?

  We are glad that we were able to resolve this issue, and will now proceed to close this thread.

  If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.

  Ask a related question Ask a new question
• Prodigy 60 points

  

  Abu Bakar

  

  • Jun 2, 2017 6:58 PM

  In reply to Abu Bakar:

  Voltage(V) --------Clock Speed(MHz)
  2.3------------------ 8.2
  2.5------------------ 8.1
  3.0------------------ 8.0
  3.5------------------ 7.9

  • Locked
  • Cancel

  Do you have another question?

  We are glad that we were able to resolve this issue, and will now proceed to close this thread.

  If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.

  Ask a related question Ask a new question
• Intellectual 965 points

  

  Dubnet

  

  • Jun 2, 2017 7:30 PM

  In reply to Abu Bakar:

  If I read the information on page 30 of the MSP430G2553 data sheet correctly, that actually falls into the specification for power supply rejection error of the DCO at +/-3% from 2.2 to 3.6V

  • Locked
  • Cancel

  Do you have another question?

  We are glad that we were able to resolve this issue, and will now proceed to close this thread.

  If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.

  Ask a related question Ask a new question