MC68302 about HALT signal

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MC68302 about HALT signal

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荒谷優貴
Contributor I

When touch passive probe HALT signal, HALT signal is Low.(stand up in 2V at 1.5us intervals)

When not touch passive probe HALT signal, HALT signal is High(not double bus error.)

When passive probe touch HALT signal for mmeasure,Why HALT signal is Low?

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TomE
Specialist II

> Why HALT signal is Low?

Because you're pulling it low.

You should provide more details on what your board is and what is going wrong.

What value pullup resistor does your hardware have on the CPU Halt pin? For an example see the schematic here:

http://cache.freescale.com/files/32bit/doc/fact_sheet/MC68302FADSUM.pdf?fasp=1&WT_TYPE=Reference%20M...

What is the CAPACITANCE of your probe? What is the voltage on the HALT pin when you connect a capacitor from it to ground where the capacitor has zero volts on it?

My Tek probes are 16pf (/10) or 95pF (/1). So connecting them to a 10k pullup would generate a 160ns or 950ns low going pulse.

Tom

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