added some graphics

6 files changed, 54 insertions, 51 deletions

diff --git a/README.md b/README.md
index b65fea9..010dd4c 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,7 @@ The board used in this project is a [Tang Nano 9K](https://wiki.sipeed.com/hardw
 * `make clean` to clean build files.
 * `gtkwave build/waveform_*.vcd` to view waveform of corresponding testbench.
 * `make rom` to compile source files in prog/src, link and generate rom file.
+* `make objdump` to disassemble rom file.
 * `make wave` to view waveform of cpu running build/rom.hex.
 
 ## Tools
@@ -48,7 +49,7 @@ The board used in this project is a [Tang Nano 9K](https://wiki.sipeed.com/hardw
 * I-type: addi, andi, ori, xori, slti, sltiu, slli, srli, srai, lw
 * S-type: sw
 * B-type: beq, bne, blt, bge, bltu, bgeu
-* U-type:
+* U-type: lui, auipc
 * J-type: jal, jalr
 
 ## Resources
@@ -59,7 +60,13 @@ The board used in this project is a [Tang Nano 9K](https://wiki.sipeed.com/hardw
 * [Operating Systems: Three Easy Pieces by Remzi and Andrea Arpaci-Dusseau](https://pages.cs.wisc.edu/~remzi/OSTEP/)
 * [Example RISCV Cores](https://github.com/yunchenlo/awesome-RISCV-Cores)
 
-
+## Design
+### Microarchitecture
+![Microarchitecture](res/microarchitecture.jpg)
+### Control Unit FSM
+![Control Unit FSM](res/control_unit_fsm.jpg)
+### Memory Layout
+![Memory Layout](res/memory_layout.jpg)
 ## Waveform Example
 
 Here we can see the waveforms of various internal signal of the CPU, executing the following instructions:
diff --git a/prog/link.ld b/prog/link.ld
index ae0988f..5c9926c 100644
--- a/prog/link.ld
+++ b/prog/link.ld
@@ -1,7 +1,7 @@
 MEMORY
 {
-  ROM (rx)  : ORIGIN = 0x00010000, LENGTH = 4K
-  RAM (rwx) : ORIGIN = 0x00100000, LENGTH = 4K
+  ROM (rx)  : ORIGIN = 0x00010000, LENGTH = 4K /* (1024 words, 0x0001_0000 to 0x0001_FFFF) */
+  RAM (rwx) : ORIGIN = 0x00100000, LENGTH = 4K /* (1024 words, 0x0010_0000 to 0x0010_FFFF) */
 }
 
 ENTRY(_start)
@@ -12,61 +12,61 @@ SECTIONS
   {
     _stext = .;
     . = ORIGIN(ROM);
-    _start = .;       /* Entry point address */
-    KEEP(*(.text.startup)) /* Ensure startup code is kept */
-    *(.text)          /* .text sections (code) */
+    _start = .;                /* entry point address */
+    *(.text.startup)
+    *(.text)                   /* .text sections (code) */
     *(.text.*)
     . = ALIGN(4);
-    _etext = .;       /* End of code section, needed for copying .data */
+    _etext = .;                /* end of code section */
   } > ROM
 
   .rodata :
   {
-    *(.rodata)               /* Read-only data */
+    *(.rodata)                 /* Read-only data */
     *(.rodata.*)
   } > ROM
 
   .data : 
   {
-    _sidata = LOADADDR(.data); /* Start address of .data section in ROM */
+    _sidata = LOADADDR(.data); /* start address of .data section in ROM */
     . = ALIGN(4);
-    _sdata = .;       /* Start of .data section in RAM */
-    *(.data)          /* .data sections (initialized data) */
+    _sdata = .;                /* start of .data section in RAM */
+    *(.data)                   /* .data sections (initialized data) */
     *(.data.*)
     *(.sdata)                  /* .sdata sections (small initialized data) */
     *(.sdata.*)
     . = ALIGN(4);
-    _edata = .;       /* End of .data section in RAM */
+    _edata = .;                /* end of .data section in RAM */
   } > RAM AT > ROM
 
   .bss :
   {
     . = ALIGN(4);
-    _sbss = .;        /* Start of .bss section */
-    *(.bss)           /* .bss sections (zero-initialized data) */
+    _sbss = .;                 /* start of .bss section */
+    *(.bss)                    /* .bss sections (zero-initialized data) */
     *(.bss.*)
     *(.sbss)                   /* .sbss sections (small zero-initialized data) */
     *(.sbss.*)
     *(COMMON)
     . = ALIGN(4);
-    _ebss = .;        /* End of .bss section */
+    _ebss = .;                 /* end of .bss section */
   } > RAM
 
   .heap (NOLOAD) :
   {
     . = ALIGN(4);
-    _sheap = .;       /* Start of heap */
-    . = . + 1K;       /* Size of heap (adjust as needed) */
-    _eheap = .;       /* End of heap */
+    _sheap = .;                /* start of heap */
+    . = . + 1K;                /* size of heap */
+    _eheap = .;                /* end of heap */
     . = ALIGN(4);
   } > RAM
 
   .stack (NOLOAD) :
   {
     . = ALIGN(4);
-    _sstack = .;      /* Start of stack */
-    . = . + 1K;       /* Size of stack (adjust as needed) */
-    _estack = .;      /* End of stack */
+    _sstack = .;              /* start of stack */
+    . = . + 1K;               /* size of stack */
+    _estack = .;              /* end of stack */
     . = ALIGN(4);
   } > RAM
 
diff --git a/prog/src/startup.c b/prog/src/startup.c
index 32aa131..c09f221 100644
--- a/prog/src/startup.c
+++ b/prog/src/startup.c
@@ -1,39 +1,35 @@
-extern unsigned int _sidata; /* Start address for the .data section in ROM */
-extern unsigned int _sdata;  /* Start address for the .data section in RAM */
-extern unsigned int _edata;  /* End address for the .data section in RAM */
-extern unsigned int _sbss;   /* Start address for the .bss section */
-extern unsigned int _ebss;   /* End address for the .bss section */
-extern unsigned int _estack; /* End address for the stack section */
+extern unsigned int _sidata; // start of .data section in ROM
+extern unsigned int _sdata;  // start of .data section in RAM
+extern unsigned int _edata;  // end   of .data section in RAM
+extern unsigned int _sbss;   // start of .bss section
+extern unsigned int _ebss;   // end   of .bss section
+extern unsigned int _estack; // end   of .stack section (stack top)
 
-void main(void);             /* The main function declaration */
-void _start(void) __attribute__((section(".text.startup"), naked)); /* The entry point */
+void main(void); // main function declaration
+
+void _start(void) __attribute__((section(".text.startup"), naked)); // entry point, cpu starts executing from here
 
 void _start(void)
 {
-    unsigned int *src, *dest;
-
-    /* Copy .data section from ROM to RAM */
-    src = &_sidata;  /* ROM address of the .data section */
-    for (dest = &_sdata; dest < &_edata;)
-    {
-        *dest++ = *src++;
-    }
-
-    //while(1);
+  unsigned int *src, *dst;
 
-    /* Zero initialize .bss section */
-    for (dest = &_sbss; dest < &_ebss;)
-    {
-        *dest++ = 0;
-    }
+  // copy .data section from ROM to RAM
+  src = &_sidata;
+  for (dst = &_sdata; dst < &_edata;) {
+    *dst++ = *src++;
+  }
 
+  // zero initialize .bss section
+  for (dst = &_sbss; dst < &_ebss;) {
+    *dst++ = 0;
+  }
 
-    /* Initialize stack pointer */
-    asm volatile ("la sp, _estack");
+  // initialize stack pointer
+  asm volatile ("la sp, _estack");
 
-    /* Call the main function */
-    main();
+  // call main function
+  main();
 
-    /* If main returns, loop forever */
-    while (1);
+  // halt
+  while (1);
 }
diff --git a/res/control_unit_fsm.jpg b/res/control_unit_fsm.jpg
new file mode 100644
index 0000000..a6b2bfc
--- /dev/null
+++ b/res/control_unit_fsm.jpg
diff --git a/res/memory_layout.jpg b/res/memory_layout.jpg
new file mode 100644
index 0000000..893aa4d
--- /dev/null
+++ b/res/memory_layout.jpg
diff --git a/res/microarchitecure.jpg b/res/microarchitecure.jpg
new file mode 100644
index 0000000..f182fe8
--- /dev/null
+++ b/res/microarchitecure.jpg