SECTION 15.1: PROGRAMMING THE 8255
1. Find the control byte if all ports are inputs.
2. Find the control byte for PC = in, PB = out, and PA = out.
3. True or false. To avoid aliases, we must decode addresses A0 - A15.
4. Can 86H be the base address for port A of the 8255?
5. Why do we use the MOVX instruction to access the ports of the 8255?
4. It cannot since we must have Al = 0 and AO = 0 for the base address.
5. The MOVX instruction allows access to external memory and 8255 is mapped as memory-mapped I/0.
SECTION 15.2: 8255 INTERFACING
1. Modify the stepper motor program to turn counterclockwise.
2. True or false. In programming the LCD via an 8255 (without checking the busy flag), port A is always an output port.
3. True or false. In the LCD connection to the 8255, we must have a long delay before issuing the next data if we are not checking the busy flag.
1. "RR A" is changed to "RL A".