136 lines
4.5 KiB
Markdown
136 lines
4.5 KiB
Markdown
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30pin-simm-ram-arduino
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======================
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Library to interface with 30-pin simm ram using an atmega328p on Arduino
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Copyright (C) 2014 - Rafael Ignacio Zurita <rafaelignacio.zurita@gmail.com>
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LICENSE : read below.
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**This project got a got article in HACKADAY!** : http://hackaday.com/2014/04/09/using-simms-to-add-some-extra-ram-on-your-arduino-uno
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Introduction
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------------
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This repo contains the library to interface with 30-pin simm ram modules,
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like the ones which were used in AT (286), 386, 486, Macintosh Plus,
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Macintosh II, Quadra, Atari STE and Wang VS systems. Using an atmega328p on
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Arduino.
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It will give you extra RAM to store and restore dynamic data
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in your sketches.
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__Pictures and Video__ : on the bottom
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This work was inspired and based for the great hack to run Linux
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on a 8bit MCU by Dmitry Grinberg
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http://dmitry.gr/index.php?r=05.Projects&proj=07.%20Linux%20on%208bit
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The code is also based in the __KM41C4000D 4M x 1Bit CMOS Dynamic RAM datasheet__ http://pdf.datasheetcatalog.com/datasheets/400/250350_DS.pdf
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License
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-------
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The library has two versions : C and avr assembler version. Both for
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atmega328p (Arduino).
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Both version are free software, you can redistribute it and/or modify
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it under the terms of the GNU General Public License version 2 as
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published by the Free Software Foundation.
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Read the LICENSE file for details, and the README file under the assembler
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version directory.
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Usage
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-----
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WARNING: using this kind of RAM will put your Arduino CPU to refresh the SIMM RAM
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data part of the time. It means that your sketches (programs) could run
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a little slower than before.
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Also, we need to use most of the Arduino pins to be soldered with SIMM RAM pins
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so there will be just few available extra pins for your project.
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1. Connect the 30-pin SIMM RAM like schematic.txt file explains.
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2. Copy the ram/ directory under sketchbook/libraries/.
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If you prefer using the avr assembler version for better performance
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copy the files under avr-asm-ram-version/* instead. Read the REAMDE
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file there as well.
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3. The usage of the RAM is easy. In your main code (or sketch) call ram_init()
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just once, and then ram_write() and ram_read() to store and recover
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data from SIMM RAM.
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Example
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-------
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```
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#include "ram.h"
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...
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ram_init();
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/* write one byte to RAM */
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ram_write(1, 2, 7); /*# row=1, col=2, store byte = 7 */
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/* write several bytes to RAM */
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char gb[] = "Good Bye!";
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for (i=0, i<strlen(gb), i++)
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ram_write(2, i, gb[i]); /* row=2, col=i, store byte = i of gb */
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/* read from RAM */
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c = ram_read(1, 2); /* restore byte = 7 from row=1, col=2 */
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d = ram_read(2, 0); /* restore letter "G" from row=2, col=0 */
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```
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You can use the ram_test.ino as example for using your 30-pin simm ram.
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Limitations
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-----------
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SIMM RAM has 12 bit address for rows and columns. Max RAM size here
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is 16MB. We are using just 6 pins for rows and columns, so we
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are limited to 4KB of RAM space.
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Addresses space will be of 64rows x 64columns = 4096 addresses
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1 byte each = 4KB of space.
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If you need to use more RAM you can solder the 3 analog pins remaining
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to simm ram module pins A6, A7 and A8. It will give you 256 KB of RAM space.
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References
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----------
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Dmitry code for atmega168 did not work as is.
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In order to have a proper working code we needed to read several
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datasheets. At least we studied the KM41C4000D, KM41V4000D CMOS DRAM
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datasheet and other sources of RAM chips, like
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http://www.pjrc.com/mp3/simm/datasheet.html
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and
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http://www.pjrc.com/mp3/simm/simm.html
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__KM41C4000D 4M x 1Bit CMOS Dynamic RAM datasheet__ http://pdf.datasheetcatalog.com/datasheets/400/250350_DS.pdf
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Pics
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----
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<img src="https://github.com/zrafa/zrafa.github.io/blob/master/ram-atmega328p-arduino/ram-arduino-sch.jpg?raw=true" alt="simm ram and atmega328p" width="500" height="400">
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<img src="https://github.com/zrafa/zrafa.github.io/blob/master/ram-atmega328p-arduino/ram-arduino3.jpg?raw=true" alt="simm ram and atmega328p" width="400" height="300">
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<img src="https://github.com/zrafa/zrafa.github.io/blob/master/ram-atmega328p-arduino/ram-arduino2.jpg?raw=true" alt="simm ram and atmega328p" width="400" height="300">
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<img src="https://github.com/zrafa/zrafa.github.io/blob/master/ram-atmega328p-arduino/ram-arduino.jpg?raw=true" alt="simm ram and atmega328p" width="400" height="300">
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Video
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-----
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<a href="http://www.youtube.com/watch?feature=player_embedded&v=Yah3ViEggxA"
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target="_blank"><img src="http://img.youtube.com/vi/Yah3ViEggxA/0.jpg"
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alt="arduino interfacing with simm ram module" width="320" height="240" border="10" /></a>
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