Homework Assignment 5
Due March 10, 2000

1. To your Altera program of last week add code to make the data lines to the outside bidirectional. Use Bit 5 of the control register to do this. If Bit 5 of the control register is 0, the data lines should be outputs. If Bit 5 of the control register is 1, the data lines should be inputs.
2. Add to the Altera program code to implement an interrupt. The interrupt should be the same as the interrupt on the standard parallel port, interrupting using the ACK line. Use Bit 4 of the control register to enable and disable the interrupt, just like on the standard parallel port. You can implement the interrupt using tri-state logic (disable the output when Bit 4 is low, enable when Bit 4 is high), or an open drain output (drive the open drain from VCC when Bit 4 is low, from the ACK line when Bit 4 is high).
3. Simulate the bidirectional data lines and the interrupt line. Show that they simulate correctly.