So what to 'debounce' and what not? Only the code can know. But for a pushbutton, the bouncing is usually in the kHz range. Imagine the port logig would 'debounce' an incoming SPI datastream with 16MHz Baudrate. What's wanted and what's unwanted depends on the application. There is no universal definition of what a bounce is, other than being an unwanted signal. ![]() For interrupt timing, the minimum pulse width is 20nS, so my guess is that only frequencies above 25MHz are filtered (debounced).Īnything below would limit the maximum input frequency - a debounce circuit doesn't know whether an incoming signal is a bounce or intended. However, this is limited to bounce frequencies above the specified input frequency. There are no special elements inside this block that aren't on other MSPs.ĪBout debouncing, well, the schmitt triggers do some debouncing. The logic inside teh dashed lines is present on every other MSP too but not specifically grouped. ![]() I think the term 'Pad Logic' is just a design element. Please confirm if MSP430’s “pad logic” actually does this or not.Īnd what frequency is “Pad logic”’s signal edge detection working at, or what is its clock source? If I use DCO to adjust MSP430F2274 MCLK to 1M, is edge detection clock proportional to this or not? I think it would be very advantageous if debouncing circuit can be omitted. The size of MSP430 chips as well as the final product are usually very small, and so is the total cost. Does it mean the “Pad logic” actually does some debouncing so that external debouncing circuit is not needed? The “Pad logic” in the pin diagrams shows explicitly the Hysteresis (or Schmitt trigger) symbol which seems suggesting some type of delay feature. By definition Schmitt trigger has Hysteresis characteristics, but does it do any signal level debouncing? GPIO pins on other devices also have “Edge detection logic”, but on those devices no debouncing is done by the hardware and the interrupt is extremely sensitive to transient signal level changes, so that either software or external debouncing circuit is required to eliminate spurious short pulses and to preserve only true step signal (either rising or falling). ![]() This is the same as GPIO pins on other devices does.īut I have one particular question on the Schmitt trigger. Though not defined elsewhere, I think the meaning of “pad logic” is clear: direction control, interrupt detect, and so on. Other Parts Discussed in Thread: MSP430F2274īetween page 58 and 73 of MSP430F2274 datasheet SLAS504F, diagram for each pin module contains term “Pad logic” on the upper right, and it clearly refers to the part enclosed in the dashed lines.
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