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what is the MSP430F149 / MSP430G2203 Crystal "pf" value?

Keun Hoo Rhee
Prodigy 60 points

Hi. first. my english is not good. so i hope understand my english. i'll try more good write. 

anyway, i design PCB MSP430F149, MSP430G2203

but there have little problem. and 2 MCU is different problem. 

1. MSP430F149

after write program(i'm using CCS6.0, MSP-FET430UIF) i think MCU die.

because if i try again write. can not write. 

i don't know why. but i see some internet. if XTAL pf is not good. easy to die.

so have a question. i use 8.00mhz XTAL. but there add 33pf.  it is not good?

and OSC is 32.768khz. there no have pf things. it's fine?

2. MSP430G2203

i make PCB 100pcs. but 50?70?pcs is "very slow works" i try change XTAL, MCU.

but same....

i want know where is my problem. i using XTAL is 32.768Khz. 33pf

thanks for read my question. i hope help me this problem.

thank you. i will waiting this!

  • 0
    Guru 227245 points

    The required load capacitance for a crystal depends on the crystal. So see the crystal datasheet.

    If the specified load capacitance is x, then you need (2x-1)pF from each crystal pin to GND. (-1 because of the already existing pin capacitance of the MSP pins)

    33pF is a usual value, but better check the datasheet.

    For LF crystals, the MSP offers some common load capacitance values (here, the value to select is the load capacitance itself, no formula). If the available options won’t fit, you’ll need external caps again. Or you combine internal and external (then use the formula again on the remaining load capacitance)

    It is possible to write code that locks the CPU.
    If the code causes a reset (e.g. by a password violation right at the beginning of main), this will interrupt the JTAG connection and the debugger is unable to upload a new firmware.
    It might help to try the Elprotronic software to erase the chip – it is a bit faster and this might make the difference.
    You may also try to connect to the MSPs bootstrap loader and issue a mass erase, to get rid of the offending code. Since the BSL entry is carried out before the user code is started, it remains functional even if the code immediately crashes the system.

    What do you mean with ‘very slow works’? What do you expect and what happens? What is your code? For 32kHz XTALs, usually the internal caps are sufficient (if properly configured). No need for external caps. Note that 2*33pF (+1pF for pin capacitance) result in 17pF load, which is quite much. Most watch crystals take 12pF effective load.

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