Other Parts Discussed in Thread: SN74LVC3G17, SN74LVC1G74, ADS1248, TDC1000
I've got a weird issue:
- I start a measurement (CONFIG1=c3h, all other registers at their default values, CLOCK is 16 MHz)
- in response to that, TRIGG transitions from low to high
- 500 ns later, INTB transitions from low to open (if it wasn't already open)
- 3000 ns later, START transitions from low to high (and stays high for the rest of the measurement)
- in response to that, TRIGG immediately transitions from high to low (ie, the TDC7200 does see the START edge)
- 10000 ns later, STOP transitions from low to high (and stays high)
- in about 4 out of 5 cases, measurement terminates successfully (INTB goes low)
- in about 1 out of 5 cases, nothing happens: INTB stays open and the registers indicate the TDC7200 is still measuring, without overflow.
As no overflow happens, I conclude that the TDC7200 has missed the START edge, though it makes TRIGG go low. That is, the TDC7200 both sees and ignores the START edge.
Any idea what's wrong? Is there a maximum value for the time between TRIGG and START (the datasheets lists only a nominal value, no maximum value)? Is there a maximum value for the duration of the START pulse (the datasheet lists only a minimum value)? Does START have to be low for STOP to be detected?