Added example code

README.md

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+# E220Term
+
+> Version: 1.0.20092.1 \
+> Created by: Jali <jali@orca-central.de> \
+> Last modified by: Jali <jali@orca-central.de>
+
+## About
+
+The PC-E220 was one of the last, and by far the most powerful of the 
+Sharp Pocket-Computer series.
+
+These where small computers, you could actually carry around with you, and
+use on the go. While most of them where glorified programmable pocket calculators,
+the PC-E220 came with 32KiB of RAM and a CMOS-SC7852 CPU, that was code compatible with
+the Zilog Z80A at 3.58 MHz. That made the CPU faster than an Amstrad CPC or other Z80 based
+machines of the time.
+
+While the 144x32 dot-matrix display is not very well equipped for graphics, because
+it is divided into 5x7 cells, it can print a wide range of characters, and displays
+24 characters in 4 rows. By the standards of a pocket computer, that was a lot.
+
+It comes, however, with a fully equipped serial interface, that can be used to connect to
+other systems. 
+
+This project attempts to implement a small dumb terminal, to connect to a console of a Linux
+system, just for the experience of writing some useful code for his tiny machine.
+
+## Coding
+
+The E220 has a built-in assembler, which is the target of this code.
+The goal is, to write code, that can be transferred onto the E220 and assembled 
+directly on the device. Of course any Z80 assembler should be able to assemble the code.
+Keep in mind though, that the code makes use of the built in ROM function, for example 
+for outputting characters on the screen, and therefore will only work on the E220!
+
+The src/examples section contains experimental code to use these sub routines.

src/example/char_out.asm

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+10;Outputs an "A" in the second column of the last row
+20          ORG     100H    ;Tell the assembler to start at addr. 0x100
+30START:    LD      A,41H   ;Load the letter "A" to register A
+40          LD      DE,301H ;Sets the row to 3 and the column to 1
+50          CALL    8468H   ;Calls the ```char_out``` function
+60          RET             ;Return
+70          END             ;Marks the end of the code for the assembler
+

src/example/char_out.md

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+# ```char_out```
+
+> Version: 1.0.20092.1 \
+> Created by: Jali <jali@orca-central.de> \
+> Last modified by: Jali <jali@orca-central.de>
+
+## About
+
+The ```char_out``` function is one of the built-in functions from the ROM.
+It takes a character, and writes it onto the screen, at a specific location.
+
+## Parameters
+
+```char_out``` is called through address 0x8468. It takes three parameters:
+- Register A holds the ASCII code of the character to print
+- Register DE holds the position on the screen. D is a value between 0 and 3, representing
+  the row, while E has a value between 0-23, representing the column to print in.
+
+## Example
+
+```ASM
+10;Outputs an "A" in the second column of the last row
+20          ORG     100H    ;Tell the assembler to start at addr. 0x100
+30START:    LD      A,41H   ;Load the letter "A" to register A
+40          LD      DE,301H ;Sets the row to 3 and the column to 1
+50          CALL    8468H  ;Calls the ```char_out``` function
+60          RET             ;Return
+70          END             ;Marks the end of the code for the assembler
+```

src/example/str_out.asm

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+10;output a string into the top left of the screen
+20        ORG   0100H       ;Start at addr 0x100
+30START:  LD    HL,DATA     ;Load the start address of the string
+40        LD    B,0DH       ;The length of the string (max 255 chars)
+50        LD    DE,0H       ;Start in the top left corner (D=0-3 -> row; E=0-23 column)
+60        CALL  84CDH       ;Call the str_out function in ROM
+70        RET               ;Return from call
+80DATA:   DB    'HELLO, WORLD!'
+90        END               ;End marker for the assembler
+

src/example/str_out.md

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+# ```str_out```
+
+> Version: 1.0.20092.1 \
+> Created by: Jali <jali@orca-central.de> \
+> Last modified by: Jali <jali@orca-central.de>
+
+## About
+
+The ```str_out``` function is one of the built-in functions from the ROM.
+It takes a string of characters, and writes them onto the screen, at a specific location.
+
+## Parameters
+
+```str_out``` is called through address 0x84CD. It takes four parameters:
+- Register HL holds the address of the string in memory
+- Register B holds the length of the string. This restricts the maximum length to 255.
+- Register DE holds the position on the screen. D is a value between 0 and 3, representing
+  the row, while E has a value between 0-23, representing the column to print in.
+
+## Example
+
+```ASM
+10;output a string into the top left of the screen
+20        ORG   0100H       ;Start at addr 0x100
+30START:  LD    HL,DATA     ;Load the start address of the string
+40        LD    B,0DH       ;The length of the string (max 255 chars)
+50        LD    DE,0H       ;Start in the top left corner (D=0-3 -> row; E=0-23 column)
+60        CALL  84CDH       ;Call the str_out function in ROM
+70        RET               ;Return from call
+80DATA:   DB    'HELLO, WORLD!'
+90       END               ;End marker for the assembler
+```
+