I build my driver board using L6203+L297+74HC14N
at 74hc14n input stage, I put 10k pull up ( i'm expecting my AVR to sink to make it "low" )

To test the driver board, I using AVR microcontroller to send signal clock & other inputs.. but it failed and even damage my L297 chip

there are 2 boards, the 1st is the stepper driver, the 2nd is the AVR board
each one of them use different power source & ground. could it be the problem?