Arduino sketches used in the project

The following sketches can be found in this folder:

• 6502-mega-debugger - improved version of Ben's monitor, but with major changes impacting how connections are made to 6502 computer bus and how it works internally. Currently being developed and described in detail below. USED FREQUENTLY AND WORKS
• 6502-monitor - based on Ben's monitor code with some small modifications (like clock counter I used for clock interrupt testing), to be uploaded to Arduino Mega for debugging USED FREQUENTLY AND WORKS
• 6522-monitor - similar to the above, implemented for testing of the output from VIA chip NOT TESTED FOR A LONG TIME
• address-decoder-test - my own take on the TDD principles in hardware design, described in detail here NOT TESTED FOR A LONG TIME
• bounce-counter - small program used for troubleshooting of the noise issue in monostable mode of Ben's clock module USED RECENTLY AND WORKS
• handshake-4313 - small program used to test hardware handshake with VIA, to be uploaded to ATtiny4313 NOT SURE IF STILL WORKS
• handshake-test - similar to the above, but built for Arduino Mege NOT SURE IF STILL WORKS
• irq-4313 - very small program to test IRQ handling by ATtiny4313 PROBABLY STILL WORKS
• irq-test - as above, but targeted for Arduino Mega PROBABLY STILL WORKS
• keyboard-4313 - THE MOST IMPORTANT ARDUINO SKETCH HERE - this one has to be uploaded to ATtiny4313 for PS/2 keyboard operation USED FREQUENTLY AND WORKS
• keyboard-mega - similar as above, but for Arduino Mega, not to be used, written for debugging purposes WORKS
• keyboard-detect-mega - modification of the above to implement proof-of-concept PS/2 host to device communication WORKS
• keyboard-test-4313 - first version of the code for keyboard controller, but used only to validate PS/2->AVR connection, no interaction with VIA yet. Merged with handshake-4313 to implement data transfer to VIA WORKS
• keyboard-test-mega - as above, but targeted for Arduino Mega PROBABLY WORKS

As you can see, there is plenty of unused code there, but I kept it for the record and reference. You basically need two programs for 6502 (6502-monitor to be installed on Arduino Mega for debugging and keyboard-4313 to be installed on onboard ATtiny4313 for keyboard controller operation) and another one for the clock module (bounce-counter, to be installed on Arduino Mega to confirm correct operation in monostable mode).

6502 Mega Debugger

My own version of Ben's monitor program with several additions:

• It provides clock signal to the computer, so no clock module is required,
• It has interactive interface, so you can control operation mode from within the serial terminal connected to Arduino Mega,
• While maintaining compatibility with Ben's design (single step mode and continuous execution with full system bus dumps)
• It has also high-performance mode where code is executed as fast as possible (up to 275kHz), but without dumping system bus to serial. It can be stopped manually, or upon hitting one of two possible breakpoints (defined at runtime),
• Support for SYNC line (to enable proper disassembly functionality) is corrently in development.

To use this version, you have to upload the sketch to Arduino Mega (which you should already have, when building BE6502), and connect the pins as follows:

System Bus Pin	Arduino Mega Pin
A00	22
A01	23
A02	24
A03	25
A04	26
A05	27
A06	28
A07	29
A08	37
A09	36
A10	35
A11	34
A12	33
A13	32
A14	31
A15	30
D00	49
D01	48
D02	47
D03	46
D04	45
D05	44
D06	43
D07	42
CLK	50
R/W	51
SYNC	52

You also have to disconnect clock generator (oscillator or clock module) from the system to prevent conflict. Connect to Arduino Mega using serial terminal of choice with baud rate of 57600. Stop the Go/Run operations with 's' key.

You can see the device in action here.