How does the old L293D behave with a stepper-motor and randomly switching inputs 1Y to 4Y?

[StefanL38]

Hi everybody,

in a programming thread an old adafruit motorshield V1.2 is used.
I tried to find a schematic for this motor-shield but I do not really understand the schematics I have found so far

The library for the old adafruit motorshield V1.2 seems to use a 74HC595 bitshift-register to drive the pins of the L293D. Again I do not really understand what the code is doing with the IO-pins.

So a much more practical approach than analysing is real IO-pin-switching HIGH-LOW.
And this is my question:
with a steppermotor connected to the outputs 1Y to 4Y of the L293D what will happen if the input-pins are switched on/off in random order?

Is it possible to switch the inputs 1A to 4A and EN1 / EN2, EN3/EN4 to any LOW-HIGH-combination on all input-pins without damaging the L293D-chip?

is it possible to damage the L293D-chip with an anallowed HIGH-LOW_combination or not?

best regards Stefan

[JCA34F]

l293d.pdf (496.0 KB)

[gilshultz]

The L293 is a poor chip, I do not use it but from what I understand you will not hurt it by any order of inputs but expect weird outputs. The schematic is simply showing the 595 is receiving the bits shifted out from the Arduino. Look at the labels on the shift register and the L293. But the corresponding bit number on each of the L293 inputs. You shift a byte (8 bits setting each bit you want on to a logic one and the others to a zero. Shift it into the 595 and when send the latch it will transfer the bits you sent it to its outputs.