Console now truncates input if it's too long (instead of failing to read)

README.md

@@ -1,5 +1,5 @@
 # RE6502
-
 RE6502 is an emulator for the 6502 cpu written in rust. The project comes with a very basic virtual machine for testing (it just has simple I/O functionality) as well as some test programs (find these in simple_test_machine/programs). The test programs can be built with the win2c64 (or lin2c64, or mac2c64) assembler which can be found here: https://www.aartbik.com/retro.php. Theoretically any 6502 assembler should work but win2c64 is the one I've been using for testing.
 
 # Building
+The emulator doesn't really do anything on it's own but you can build it with the normal `cargo build` or `cargo run` if you run this program it will just do some simple internal tests. There are also unit tests you can run with `cargo test`. To make better use of the emulator you'll need to use it as a component of a larger emulator/vm. Take a look a the Simple Test Machine project to see how to use the RE6502 as a component.

simple_test_machine/README.md

@@ -1,8 +1,18 @@
 
 # The Simple Test Machine
-
+The Simple Test Machine is a very basic virtual machine that uses the RE6502 as the cpu and a custom Console for simple I/O operations. There are example programs in the programs directory for reference/testing. The important memory addresses (I/O buffers, bit flags, etc) are listed in the src/machine.rs file.
 
 # Running the Simple Test Machine
-
+To build the project you can `cd simple_test_machine` then `cargo build` or `cargo run`. If you run it on it's own it will just run some basic internal test programs. To run a specific progam you can pass the name of the binary to load when the machine starts up. To do this with cargo try `cargo run -- path/to/the/program` (ex. `cargo run -- programs/bin/hello.rw`).
 
 # Assembling Programs for the Simple Test Machine
+Program binaries are not included in this repo but you can build them from the .asm files in the programs subdirectory. I've tested building these programs with the `win2c64` assembler (it also has linux `lin2c64` and mac `mac2c64` versions) that can be found here: https://www.aartbik.com/retro.php. 
+
+To use the assembler you can invoke it directly or use the `assemble.bat` script in the programs subdirectory. 
+
+## Using the assemble.bat script
+To use the assemble.bat script you'll need to cd into the programs directory: `cd programs` (or, if you're in the project root: `cd simple_test_machine/programs`) then you can run the script with `.\assemble.bat hello.asm`. The script will move the resulting binary into the bin directory.
+
+## Using win2c64 directly
+You can invoke win2c64 directly with `win2c64.exe -R my_program.asm` The `-R` option is necessary to have the assembler output the binary in the correct format.
+

simple_test_machine/programs/assemble.bat

@@ -1,8 +1,9 @@
 
+@echo off
+
 REM Usage: Drop the win2c64 directory into the same directory with this script
 REM		Directory structure should be: ./assemble.bat ./win2c64/win2c64.exe ./bin
 
-@echo off
 
 set src_file=%1
 echo assembling %src_file%

simple_test_machine/programs/echo.asm

@@ -1,6 +1,6 @@
 
 ; echo example - takes input and then prints it back out
-; This is for testing the InputConsole of the Simple Test Machine
+; This is for testing I/O of the Simple Test Machine
 ; by Joey Pollack
 
 ; assemble with win2c64 (or lin2c64, or mac2c64) using the -R option
@@ -12,7 +12,7 @@ con_out         .equ    $1100   ; console output buffer address
 con_in          .equ    $1200   ; console input buffer address
 con_flags       .equ    $009A   ; console flags address
 prt_str_flag    .equ    $0002   ; print string flag
-prmp_input_flag .equ 	$0004   ; prompt for input flag
+prmp_input_flag .equ 	$0010   ; prompt for input flag
 
 ; MAIN
 main    .org   $0200   ; program load address for the Simple Test Machine

simple_test_machine/programs/hello.asm

@@ -6,26 +6,30 @@
 ; Adapted for the RE6502 emulator simple test machine
 ; compile with win2c64 using the -R option
 
+; This example shows how to print a string to the console
+
 strout          .equ    $1100   ; console output address
 con_flags       .equ    $009A   ; console flags address
-prt_str_flag    .equ    $0002
+prt_str_flag    .equ    $0002   ; the print flag bitmask
 
 main    .org   $0200   ; program load address for the simple test machine
-        ldx    #0
-loop    lda    text,x
-        sta    strout,x    
-        inx
-        cpx    #11
-        bne    loop 
+
+        ; Copy the string into the console output buffer
+        ldx    #0           ; initialize the offset counter
+loop    lda    text,x       ; load byte from the text buffer, offset by x register   
+        sta    strout,x     ; store byte into the output buffer, offset by x register
+        inx                 ; increment the offset counter
+        cpx    #11          ; check if we've reached the end of the string - text is 11 bytes long
+        bne    loop         ; branch if we haven't reached the end yet
 
         ; null terminate the string
         lda #0           
         sta strout,x          
 
         ; Set flag to do the print
-        lda con_flags
-        ora #prt_str_flag 
-        sta con_flags   ; 0x86, 0x9A, ; Print string flag is at 0x9A
+        lda con_flags           ; load flags into accumulator
+        ora #prt_str_flag       ; set the print string flag
+        sta con_flags           ; store flags back into memory - this will trigger the print
 
         ; End the program
         rts            ; 0x60 

simple_test_machine/programs/mult10.asm

@@ -10,22 +10,22 @@ prt_str_flag    .equ    $0001   ; print string flag
         ; FAST MULTIPLY program from:
         ; http://6502.org/source/integers/fastx10.htm
 main    LDA #7      ; load 7 into the accumulator
-        ASL         ;multiply by 2
-        STA TEMP    ;temp store in TEMP
-        ASL         ;again multiply by 2 (*4)
-        ASL         ;again multiply by 2 (*8)
+        ASL         ; multiply by 2
+        STA TEMP    ; temp store in TEMP
+        ASL         ; again multiply by 2 (*4)
+        ASL         ; again multiply by 2 (*8)
         CLC
-        ADC TEMP    ;as result, A = x*8 + x*2
+        ADC TEMP    ; as result, A = x*8 + x*2
 
-        ; PRINT RESULT
+        ; print result
         STA strout      ; store A into the console output address
         LDX #0          ; 0xA2, 0x00, ; null terminator
         STX strout+1    ; store null terminator to output addr + 1
 
         ; Set flag to do the print
-        LDA con_flags    ; load the current console flag set
+        LDA con_flags     ; load the current console flag set
         ORA #prt_str_flag ; turn on the print string flag
-        STA con_flags    ; store the flags back in memory
+        STA con_flags     ; store the flags back in memory
 
         ; End the program
         RTS            ; 0x60 

simple_test_machine/programs/mult10_orig.asm

@@ -1,29 +0,0 @@
-
-; Multiply 7 with 10 and print the result
-; For testing this program was assembled with c64 (using the -R option):
-; https://www.aartbik.com/MISC/c64.html
-
-        ; FAST MULTIPLY program from:
-        ; http://6502.org/source/integers/fastx10.htm
-main    LDA #7      ; load 7 into the accumulator
-        ASL         ;multiply by 2
-        STA TEMP    ;temp store in TEMP
-        ASL         ;again multiply by 2 (*4)
-        ASL         ;again multiply by 2 (*8)
-        CLC
-        ADC TEMP    ;as result, A = x*8 + x*2
-
-        ; PRINT RESULT
-        STA $A0          ; 0x85, 0xA0, ; store A into the console output address
-        LDX #0           ; 0xA2, 0x00, ; null terminator
-        STX $A1          ; 0x86, 0xA1, ; store null terminator to output addr + 1
-
-        ; Set flag to do the print
-        LDX #1           ; 0xA2, 0x01,  
-        STX $9F          ; 0x86, 0x9F, ; Print byte flag is at 0x9F
-
-        ; End the program
-        RTS            ; 0x60 
-
-        ; Variables
-        TEMP    .byte 0

simple_test_machine/src/machine.rs

@@ -3,25 +3,35 @@
 use std::{io, str};
 
 //|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
-//				MEMORY ADDRESSES AND FLAGS
+//				MEMORY ADDRESSES AND FLAG MASKS
 //|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
-const PROGRAM_START_ADDR: u16 = 0x0200;     // Program code starts on page 2
-const CPU_RESET_START_ADDR: u16 = 0xFFFC;   // This is where the cpu looks for the address to start executing code at
 
-pub const OUTPUT_BUF_ADDR: u16 = 0x1100;    // Output buffer -- Put values to be printed at this location!
-pub const INPUT_BUF_ADDR: u16 = 0x1200;     // Input buffer
-pub const INPUT_BUF_SIZE: u16 = 0x00FF;     // Input buffer is 255 bytes
+// CPU Addresses
+const PROGRAM_START_ADDR:   u16 = 0x0200;     // Program code starts on page 2
+const CPU_RESET_START_ADDR: u16 = 0xFFFC;     // This is where the cpu looks for the address to start executing code at
 
+// Console Addresses
+pub const OUTPUT_BUF_ADDR:  u16 = 0x1100;     // Output buffer -- Put values to be printed at this location!
+pub const INPUT_BUF_ADDR:   u16 = 0x1200;     // Input buffer
+pub const INPUT_BUF_SIZE:   u16 = 0x00FF;     // Input buffer is 255 bytes
 pub const CONSOLE_FLAGS_ADDR:   u16 = 0x009A; // Grouping all of the console flags into a single byte
-pub const PRINT_BYTE_FLAG:      u8 = 0x01;    // Then set one of these flags to trigger the print
-pub const PRINT_STR_FLAG:       u8 = 0x02;    //      and indicate what type is being printed.
-pub const READ_LINE_FLAG:       u8 = 0x04;    // Set this flag to request user input from the keyboard
-pub const READ_OVERFLOW_FLAG:   u8 = 0x08;    // This flag is set after reading input if there is too much input for the buffer
+
+// Console Flag Masks
+pub const PRINT_BYTE_FLAG:      u8 = 0x01;    // Trigger printing a single byte
+pub const PRINT_STR_FLAG:       u8 = 0x02;    // Trigger printing a string (continues printing bytes until a null byte is encountered)
+pub const READ_LINE_FLAG:       u8 = 0x10;    // Set this flag to request user input from the keyboard
+pub const READ_OVERFLOW_FLAG:   u8 = 0x20;    // This flag is set after reading input if there is too much input for the buffer
 
 /////////////////////////////////////////////////////////////////////
 //				BUS
 /////////////////////////////////////////////////////////////////////
+
 use re6502::r6502::{R6502, Bus, Flags};
+
+// The Bus is how you connect other components to the RE6502 cpu.
+// At minimium the read() and write() traits must be implement for the Bus.
+// The following is a very basic Test Bus implementation.
+
 struct TBus
 {
     memory: [u8; 64 * 1024]
@@ -122,6 +132,9 @@ impl Console
         let mut value = bus.read(CONSOLE_FLAGS_ADDR);
         if (value & READ_LINE_FLAG) != 0
         {
+            // reset the flag
+            value &= !(READ_LINE_FLAG);
+
             let mut buffer = String::new();
             let stdin = io::stdin();
             stdin.read_line(&mut buffer).expect("Failed to read input from the console");
@@ -129,55 +142,37 @@ impl Console
             // Make sure the string will fit in the input buffer
             if (buffer.len() + 1) as u16 >= INPUT_BUF_SIZE
             { 
-                // TODO: Change this to set an error flag instead of printing. This way
-                //          the program can detect and handle these errors.
-                
-                // reset the read flag and set the overflow flag
-                value &= !(READ_LINE_FLAG);
+                // The input is too large for the buffer so
+                //  set the overflow flag
                 value |= READ_OVERFLOW_FLAG;
-                bus.write(CONSOLE_FLAGS_ADDR, value);
-
-                println!("ERROR: Console cannot store input string into memory, string is too large");
-                return;
             }
 
             // Store input in the input buffer
             for (i, byte) in buffer.chars().enumerate()
             {
+                // Truncate the input if it's too large for the buffer
+                if i as u16 >= INPUT_BUF_SIZE
+                {
+                    break;
+                }
+
                 bus.write(INPUT_BUF_ADDR + (i as u16), byte as u8);
             }
 
             // Add the null byte to the end
             bus.write(INPUT_BUF_ADDR + buffer.len() as u16, 0);
 
-            // reset the flag
-            value &= !(READ_LINE_FLAG);
+            // store the flags back into memory
             bus.write(CONSOLE_FLAGS_ADDR, value);
 
         }
     }
 }
 
-//|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
-//				CONSOLE INPUT
-//|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
-
-
-struct InputConsole {}
-
-impl InputConsole
-{
-    
-}
-
-
-
 /////////////////////////////////////////////////////////////////////
 //				MACHINE
 /////////////////////////////////////////////////////////////////////
 
-
-
 pub struct TestMachine
 {
     bus: TBus,