Added a section to the memory map for the video memory.

chapter 1.tex

@@ -1,7 +1,7 @@
 \chapter{Introduction}
-This is an attempt to distill what I know about how computers work into some kind of emulator / simulator. I'm curious to see if what I know at the moment is enough to allow me to emulate a general purpose computer. It turns out that it take quite a different skillset compared to writing web applications or desktop applications. But I realize that, while I understand the concepts that underpin what I do day to day, I don't have an intuitive understanding of the hardware. This has become painfully evident pretty much immediately after I started this project. An ISA should be simple, add, subtract, copy, etc., but the you have to consider the state the processor will be in after each instruction.
+This is an attempt to distill what I know about how computers work into some kind of emulator / simulator. I'm curious to see if what I know at the moment is enough to allow me too emulate a general purpose computer. It turns out that it take quite a different skill set compared to writing web or desktop applications. But I realize that, while I understand the concepts that underpin what I do day to day, I don't have an intuitive understanding of the hardware. This has become painfully evident pretty much immediately after I started this project. An ISA should be simple, add, subtract, copy, etc., but then you have to consider the state that the processor will be in after each instruction.
 \section{Registers}
-Thirty-two general purpose registers are available for program code to use however it wishes. The base name for the general purpose registers is \quotes{r} follows by an unpadded number, such as \quotes{r28}. These numbers do not follow a zero-based index scheme, \quotes{r29} is the twenty-ninth register. Using the base name implies full width, a \quotes{word}, when reading or writing from or to the register respectively.
+Thirty-two general purpose registers are available for program code to use however it wishes. The base name for the general purpose registers is \quotes{r} follows by an unpadded number, such as \quotes{r8}. These numbers do not follow a zero-based index scheme, \quotes{r29} is the twenty-ninth register. Using the base name implies full width, a \quotes{word}, when reading or writing from or to the register respectively.
 
 In addition to the general purpose registers there is also a base pointer (bp), stack pointer (sp) and an instruction pointer (ip). The base pointer and the stack pointer may be set directly using the \hyperref[sec:mov]{mov} instruction, which allows the programmer to set up a stack frame. The instruction pointer can only be set with a branching operation like \hyperref[sec:jmp]{jmp} or a call to a subroutine with the \hyperref[sec:call]{call} instruction. One final register that can only be indirectly set is the \quotes{flags} register. This register, like the others, is one word wide meaning it can store thirty-two flags. Currently only three flags are present, the Zero, Underflow and Overflow flags. These flags are only affected by arithmetic operations and generally read by branching instructions like \hyperref[sec:jmp]{jmp}.
 
@@ -51,7 +51,7 @@ In addition to the general purpose registers there is also a base pointer (bp),
 \end{description}
 
 \section{Memory}
-The memory layout is quite simple, much like many modern machines it is a linear memory map. The address bus is thirty-two bits wide, the same width of the data bus, meaning at most there is 2\textsuperscript{32} of addressable memory. Like contemporary machines the top of memory starts at address 0x00000000 and grows downward toward 0xFFFFFFFF.
+The memory layout is quite simple, much like many modern machines it is a linear memory map. The address bus is thirty-two bits wide, the same width of the data bus, meaning at most there is 2\textsuperscript{32} of addressable memory. Like contemporary machines the top of memory starts at address 0x00000000 and grows downward toward 0xFFFFFFFF. By default the memory is mapped as shown in Figure \ref{fig:memorylayout}.
 
 \begin{figure}
 	\begin{tikzpicture}
@@ -61,6 +61,9 @@ The memory layout is quite simple, much like many modern machines it is a linear
 		\node (top) at (memory.north east)[right] {0x00000000};
 		\node at (memory.south east)[right] {0xFFFFFFFF};
 		
-		\draw[dashed] ($(memory.north west)-(0,0.5)$) node[left] {0x20000} -- ($(memory.north east)-(0,0.5)$) node[midway, above] {Firmware};
+		\draw[dashed] ($(memory.north west)-(0,0.5)$) node[left] {0x200000} -- ($(memory.north east)-(0,0.5)$) node[midway, above] {Firmware};
+		\draw[dashed] ($(memory.north west)-(0,1.25)$) -- ($(memory.north east)-(0,1.25)$)  node[right] {0x275300 (800x600)} node[midway, above] {VRAM};
 	\end{tikzpicture}
+	\caption{Memory Map \& Layout}
+	\label{fig:memorylayout} % https://www.overleaf.com/learn/latex/Referencing_Figures
 \end{figure}