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