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MSP430f5659: what is the difference in maximum System Clock and max Oscillator frequency?

seb
Genius 4170 points
Part Number: MSP430F5659

Hi there,

I just, after using MSP430 series for a couple of years now, stumbled over the following:

In various Datasheets it states something like this:

16-Bit RISC Architecture, Extended Memory,
up to 20-MHz System Clock

and after that the Unified Clock System ( UCS) :

Unified Clock System for up to 160 Segments
– FLL Control Loop for Frequency •
Stabilization Operations
– Low-Power Low-Frequency Internal Clock
Source (VLO) Programming Voltage Needed
– Low-Frequency Trimmed Internal Reference •
– 32-kHz Crystals (XT1) Switch
– High-Frequency Crystals Up to 32 MHz
(XT2) • For Complete Module Descriptions, See th

So how can I read this?

I always used ( for another series F5529 )

a 24 MHz oscillator which is well in specs, but could I have gone faster?

So I need a maximum MCLK of the given maximum system clock?

But I can use a higher frequency for the other clocks?? like SMCLK?

and another point: I just read about the DCO beeing a facotr 10 above that anyway, with of course diminished accuracy,

so how many of you do run their systems on the DCO with somewhat 100 MHz?

Thanks for your insights,

seb

  • 0
    Guru 34483 points

    No, it is not 16-bit. MSP430F5659 is with CPUXv2, 20-bit registers and assembler instructions. Some of 20-bit assembler instructions (named in family user guide 6.6.4, as address instructions) can be executed in one cycle.

    XT2 can be used directly or divided as clock source, per datasheet up to 32 MHz. However, I didn't found any problem with 48 MHz XT2.

    Maximum MCLK for MSP430F5659 per datasheet is 20 MHz. I done some overclocking tests for MSP430F5xx/6xx, and it is possible to run (some of them, depending on used peripherals) on doubled datasheet MCLK. From my experience, for overclocking is better to use XT2 directly, and not DCO.

    http://forum.43oh.com/topic/3906-msp430f5xx-overclocking/

    Also, MCLK can be pushed (over datasheet value) only in short period of time, when there is need for more horse power. For example I use it for logic analyzer with 24 MHz sampling (DMA with 48 MHz MCLK from XT2, USB is working with bypassed PLL).

    http://forum.43oh.com/topic/3909-msp430f550x-based-logic-analyzer/?do=findComment&comment=69255

    Some peripherals can be overclocked without boosting clocks. For example, my frequency meter with 24 MHz XT2 / MCLK, was able to measure 48 MHz on timer input pin.

    http://forum.43oh.com/topic/3317-msp430f550x-based-frequency-meter/?do=findComment&comment=35453

    All course, this is all for your own pleasure, but if you want to produce and sell it, than it is better (from my point of view) to switch to low cost 48 MHz Cortex-M0+.

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