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MSP430F6723: Generic I/O Port max Frequency.

Part Number: MSP430F6723

Hi,

in my application I need to generate and read a clock generated by firmware. What is the maximum frequency at which a generic I/O port could opperate. Thank you.

 Regards.

  • The maximum pin switching speed is given in data sheet (SLAS731D) Table 5-6; it says (effectively) "as fast as the CPU clock".

    As an existence-proof, it is possible to put SMCLK out on PJ.0 [Ref data sheet Table 6-80]. This doesn't give you any choice of frequency, but you can turn it on/off using PJSEL.

    If you want to generate a clock using software, you should estimate maybe 3-5 clocks for each transition, and double that to get a full cycle period, so maybe MCLK/9. As a practical matter, you'll eventually have to loop (branch) so you'll need to slow the loop to get a consistent frequency.

    Your best bet is a timer, which can give you SMCLK/2 max, but you can adjust it.

    Does your mention of "read"ing mean that your MCU needs to interpret this clock as well? Doing that would be quite a bit more expensive.

  • Fastest port write (assembler instruction) will take 3 CPU cycles, and read (assembler instruction) 2 CPU cycles. Also DMA can be used for coping samples from RAM/flash to port or from port to RAM, and each operation (one DMA copy) will take 2 CPU cycles (CPU is stopped during this proccess).