Question
Microprocessor - Motorola 68k assembly language
1. (Hardware) An 8 bit printer port is at location $2000. CPU will input a BUSY signal generated by the printer. When high, busy signal indicates that the printer is not ready for next byte of information. Demonstrate your port design and clearly label lines attached to the printer.
2. Implement your plan using a user vectored interrupt number 3. Use busy line from the printer to trigger the interrupt. The printer interrupt level is 2. Explain the extra hardware to make this work.
3. (Software) Show mainline and service routine flowchart. Mainline will set up everything to allow interrupt to occur. Guess the service routine is at $5678, mainline is at $4000, and the stack is at $6000. The service routine software will call a subroutine called GETBYTE that gets a byte of data from register D0 and sets it to the printer. Your flow charts will show all program loops and port entrance.