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Added example code

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Alexander Noack
2020-04-02 23:44:05 +02:00
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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.

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src/example/char_out.asm Normal file
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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

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src/example/char_out.md Normal file
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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
```

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src/example/str_out.asm Normal file
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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

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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
```