There is no excuse for haphazard, dangerous, "last resort" techniques when dealing with a client's data. AISI, this case could have been solved with a logical, "first resort" approach. At the very least I would expect that professionals should take the time to learn something about electronics before playing with it. You owe it to your customers.
I have seen numerous "trial and error" threads that make me cringe. For example, one prominent forum member intentionally reversed the power supply connections to an unknown NAND after his initial attempt failed to detect it. The correct solution in such cases is to examine the PCB and note the connectivity of the NAND's bypass capacitors, then, if possible, measure the capacitor voltages.
Another horror story was when another prominent forum member soldered an unknown NAND, with a non-standard package, onto a regular ONFI jig, with the result that supply rails were wired to data pins. As before, the proper approach would have been to refer to the PCB and determine the NAND's pinout with reference to its controller and adjacent capacitors. But that requires time and effort ...
It appears that the solution in the present case was to short the R/B* (Ready/Busy*) pin to ground. This pin is "open drain" and is
designed to be switched directly to ground (as are "open collector" pins). Therefore, all one needs to do is to locate, with a DMM or by visual inspection, a test point which connects to pin #7 (R/B* for a standard ONFI NAND). One can then safely short this test point to ground.
https://en.wikipedia.org/wiki/Open_collectorWhen the NAND is in the Busy state, its open drain (or open collector) output is driven to ground via a transistor switch. Conversely, when the NAND is in the Ready state, this same switch is open.
Code:
open collector open drain
VCC VCC VCC
+ + +
| | |
| | |
.-. pullup .-. pullup .-. pullup
| | resistor | | resistor | | resistor
| | | | | |
'-' '-' '-'
Ready/Busy* | Ready/Busy* | Ready/Busy* |
o o o
.--------|--. .--------|--. .--------|--.
| C| | | D| | | | |
| | | | | | | | |
| |/ | | |-+ | | | |
| B -| | NPN | G | | N-channel | \ |
| |> | BJT | ->|-+ | JFET | \ |
| | | | | | | switch | |
| E| | | S| | | | |
'--------|--' '--------|--' '--------|--'
NAND | NAND | NAND |
=== === ===
GND GND GND
B = base G = gate off = Ready
C = collector D = drain on = Busy*
E = emitter S = source
As you can see, if you were to short the two ends of the external pullup resistor, and if the NAND were in the Busy state, you would be connecting Vcc directly to ground via the closed switch. This could seriously damage, or destroy, the switch.