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This lab we will finish up wiring the Proto-board computer and continue testing it with increasing complexity.
- Put in the RAM chip and check that the MPU/EPROM/DISPLAY test program still works. Previously you tested this program with the RAM chip removed.
- Burn a new EPROM with the RAM test program. Check that this program counts. If not, there is a problem with your RAM circuitry (or perhaps with the RAM program). Show this to your lab instructor, who will make a note of a working RAM test on the progress sheet.
- After RAM is working, test interupts using the INTERRUPT test program.
When this program is working the displays count as before. If during
the count the /IRQ line is grounded and released the display will appear
to restart beginning with a count of 01. Show this to your lab instructor, who will make a note of a working INTERRUPT test on the progress sheet.
- Next you need to check out the VIA. Write your own program as discussed in class to check the VIA.
Set port B of the VIA to output. Set port A of the VIA to input.
Connect port B to port A. (wire PB0 to PA0, PB1 to PA1, etc.) Burn and
test the program. If all is well the display will count as before.
Disconnect the lowest port line (PB0 - PA0) and observe the count. The
count should jump by two rather than by one as before. Show this to your lab instructor, who will make a note of a working VIA test on the progress sheet. What happens if you ground PA0? Why?
- Now you need to check out the ACIA using the ACIA test program.
The ACIA test program is designed to test the ACIA chip with the 6502
computer using PuTTY. When properly functioning the test program counts
up (in ASCII character order) on the terminal window while keystroke
codes are sent from the terminal to the TIL displays. Serial format is
set via the command, set control registers to the following: no parity,
no echo, no Tx/Rx interrupts. 8-N-1, 9600 baud. No handshaking or flow
control is employed. Connect the ACIA Tx to FTDI cable Rx and vice
versa. If using a buffer, connect with buffer facing the direction of
information flow. Also, a ~10k pull-up is needed on the ACIA Rx pin.
FTDI cable ground must also be wired to the 6502 computer ground. IMPORTANT: to ensure reliable serial communication, confirm that the /CTS, /DSR, and /DCD pins are all pulled LOW. View the transmit and receive signals on the oscilloscope to observe the ASCII code signal. Show this to your lab instructor, who will make a note of a working ACIA test on the progress sheet.
- Now wire up power-up reset circuit and connect it to the /RES line of the CPU. DON'T
FORGET TO REMOVE THE OLD /RES LINE FROM THE 'PULSE SWITCH' ON YOUR
TRAINER. NOT ONLY IS IT NOT NEEDED, ITS PRESENCE WILL INTERFERE WITH THE
POWER-UP RESET CIRCUIT. If this circuit is working the computer should now begin counting as soon as the power is applied. Show this to your lab instructor, who will make a note of a working power-on reset circuit on the progress sheet.