LAB 6
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 and control registers to the following: no parity, no echo, no Tx/Rx interrupts. 8-N-1, 9600 baud. No handshaking 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. 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.