This repository contains a version of the TEDMON machine code monitor for the Foenix F256 series of computers. A number of functions useful for simple debugging are also included.
This is not meant for use by end-users, rather it is a tool a programmer may include in their own programs to call and inspect program state.
The following TEDMON commands are available. Please consult TEDMON documentation for further details.
| Command | Argument | Function |
|---|---|---|
| A | address instruction | Assembles an instruction and places it in memory |
| C | start thru with | Compares memory ranges |
| D | address | Disassembles code at address |
| F | start to value | Fills memory with byte value |
| G | address | Go (jump) to address |
| H | start to value | Hunt for bytes or string |
| J | address | JSR to subroutine |
| M | address | Dump memory |
| R | N/A | Display registers |
| T | start thru to | Copy memory range |
| X | N/A | Exit |
| $ | number | Evaluate hexadecimal number |
| + | number | Evaluate decimal number |
| & | number | Evaluate octal number |
| % | number | Evaluate binary number |
| . | address instruction | Alter disassembly |
| > | address bytes | Alter memory |
| ; | registers | Alter registers |
The F256 series provide 512 KiB of RAM, but the 65C02 can only address 64 KiB at a time. An MMU is present to provide the 65C02 with access to all RAM. This MMU has four "LUTs" or configurations where one may be active at a time. The monitor uses five-digit hexdecimal addresses, where the most significant digit is the LUT number. For instance, the address $2ABCD refers to the virtual address $ABCD as configured by LUT #2.
Two binaries are needed, monitor.bin and trampoline.bin. These must be included in the user program. The monitor takes up an 8 KiB bank of memory and may be placed anywhere in physical memory. The trampoline must be loaded at virtual address $FE00, but the physical location is irrelevant. It is up to the programmer to set this up.
The monitor will assume ownership of MMU LUT #3.
It is up to the programmer to handle interrupts and enter the monitor at the appropriate time.
A test program is also provided, the test.bin program can be loaded at address $2000. It will enter the monitor so the various monitor functions can be tested.
Several functions are available to the programmer:
| Name | Vector | Function |
|---|---|---|
| Initialize | N/A | Initializes the monitor state |
| BRK | $02 | Not yet implemented |
| NMI | $04 | Not yet implemented |
| Enter | $06 | Enter the monitor |
| SetLUT | $08 | Set up a basic text screen color LUT |
| SetFont | $0A | Copies an embedded font to the text screen font memory |
| ShowScreen | $0C | Show monitor/debug screen |
| HideScreen | $0E | Hide monitor/debug screen |
| ClearScreen | $10 | Clear screen and reset cursor position |
| CharOut | $12 | Print a character to the debug screen |
| ShowCursor | $14 | Enable cursor |
| HideCursor | $16 | Disable cursor |
| ReadChar | $18 | Read a character from the keyboard (wait) |
| TryReadChar | $1A | Read a character from the keyboard (return immediatly if none available) |
| EditLine | $1C | Use the full screen editor to return a line of input |
| EnterIfChar | $1E | Enter the monitor if key pressed |
Functions must be called through the trampoline. The trampoline provides two entry points to the programmer - Initialize and Call. All monitor functions except Initialize must be called using the Call entry point.
| Name | Vector | Function |
|---|---|---|
| Initialize | $FE06 | Initialize monitor system |
| Call | $FE09 | Call monitor function |
Initializes internal state and sets up MMU LUT #3 for monitor use.
Parameters:
A - monitor physical bank #
Call monitor function.
Parameters:
X - monitor function vector
See monitor function description for any other parameters.
Enters the monitor. The monitor will keep running until the user issues the X command.
The monitor assumes a working text screen LUT has been set up by the programmer, but if it hasn't, the LUT may be initialized with this call.
The monitor assumes a working text screen font has been set up by the programmer, but if it hasn't, an embedded font may be copied to text screen font memory by calling this function.
Enables the text screen on top of all other graphics.
Removes the text screen from view.
Clears the text mode screen (fills it with space characters) and resets the cursor position to the top left corner.
Prints a single character to the cursor's position and advances the cursor.
Parameters:
A - character to print
Special character codes:
| Code | Function |
|---|---|
| 5 | Delete to the left |
| 10 | New line |
| 13 | New line |
| 28 | Cursor left |
| 29 | Cursor right |
| 30 | Cursor up |
| 31 | Cursor down |
Enables cursor display.
Disables cursor display.
Reads a character from the keyboard. Waits until one is available.
Returns:
A - character
Reads a character from the keyboard. Returns immediatly if none is available.
Returns:
A - character or zero if none is available
Returns a line of text from the screen editor. Characters are returned one by one and terminated with the CR character ($0C)
Returns:
A - character or $0C when no more characters are available
Enters the monitor if the specified character has been input from the keyboard. Returns immediatly if not.
Input:
A - character
Portions of this software is covered by the MIT license. The source files to which the license applies are clearly.