Sega Genesis

Revision for “Sega Genesis” created on February 13, 2017 @ 14:09:02

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Sega Genesis
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The Sega Megadrive, or Sega Genesis as it was known in North America, was Sega's 16 bit console. Designed around a Motoral 68000 and Zilog Z80 pairing, which was very common at the time, the console had an elegant yet straightforward architecture which made it very easy for programmers to exploit its power. [toc] <h1>SMS Mode</h1> <div>The Sega Genesis is natively backwards compatible with the Sega Master System. In fact, most of the hardware contained in the Master System is also found in a Genesis: Z80 processor, PSG, etc...</div> <div></div> <div>To enter Master System compatibility mode, it seems that you must, at the very least, do the following (refer to the <a href="https://sites.google.com/a/db-elec.com/main/home/technical-info/Genesis/pinout">Pinouts</a> section for Genesis pin locations):</div> <div></div> <div> <table border="1" cellspacing="0"> <tbody> <tr> <td><b> Genesis Pin</b></td> <td><b> Name</b></td> <td><b> Connect to</b></td> </tr> <tr> <td> B30</td> <td> #M3</td> <td> GND</td> </tr> <tr> <td> B9</td> <td> A21</td> <td> Vcc</td> </tr> <tr> <td> B10</td> <td> A22</td> <td> GND</td> </tr> </tbody> </table> </div> <div></div> <div></div> <div>With the above connections, the cartridge port loses the #RESET signal on B27 - it now constantly outputs GND instead of a nice active-low reset pulse when the reset button is pressed. Therefore, you cannot rely on B27 for reset when in Master System compatibility mode. This is the source of much frustration for me! The cartridge can still send a reset signal to the console via pin B2 in Master System mode.</div> &nbsp; <h2>Pin Reconfiguration</h2> <div>Other Genesis pins change functions when entering Master System compatibility mode. There is very little information available on these, the information listed below was found on <a href="http://www.smspower.org/forums/viewtopic.php?t=14084" target="_blank" rel="nofollow">SMSPower.org</a> and through experimentation. The list is not exhaustive and I will keep adding to it as I discover more...</div> <div></div> <div> <table border="1" cellspacing="0"> <tbody> <tr> <td><b> Genesis Pin</b></td> <td><b> Genesis Name</b></td> <td><b> SMS Function</b></td> </tr> <tr> <td> B28</td> <td> #LDSW</td> <td> #WR</td> </tr> <tr> <td> B17</td> <td> #CE</td> <td> #M0-7</td> </tr> <tr> <td> B16</td> <td> #OE</td> <td> #RD</td> </tr> <tr> <td> B11</td> <td> A23</td> <td> #PAUSE</td> </tr> <tr> <td> B6</td> <td> A18</td> <td> #CE</td> </tr> <tr> <td> B7</td> <td> A19</td> <td> #IORQ</td> </tr> <tr> <td> B27</td> <td> #RESET</td> <td> GND</td> </tr> </tbody> </table> </div> <h1>Power</h1> <h2>Console Current Consumption</h2> <div>These values were measured on NTSC consoles using a 9V benchtop power supply. These values are averages because the actual current consumption is dynamic - though according to my experiments they don't appear to vary much.</div> <div></div> <div> <table border="1" cellspacing="0"> <tbody> <tr> <td><b> Unit</b></td> <td><b> Avg (mA)</b></td> <td> <b>Peak (mA)</b></td> <td><b> Notes</b></td> </tr> <tr> <td> Model 1 HD Graphics</td> <td> 700</td> <td> 700</td> <td> Measured with and without a game inserted (Sonic 2), didn't seem to make a difference.</td> </tr> <tr> <td> Model 1 Sega CD</td> <td> 500</td> <td> 1000</td> <td> Peak occurs right after booting. The Sega CD does not power up if a Genesis cartridge is inserted.</td> </tr> <tr> <td> Model 2 Sega CD</td> <td> 500</td> <td> 1000</td> <td> Peak occurs right after booting. The Sega CD does not power up if a Genesis cartridge is inserted.</td> </tr> <tr> <td> Model 2 Genesis</td> <td> 300</td> <td> 300</td> <td> Measured with and without a game inserted (Sonic 2), didn't seem to make a difference.</td> </tr> <tr> <td> 32X with 32X game</td> <td> 350</td> <td> 350</td> <td> Measured with Doom</td> </tr> <tr> <td> 32X with Genesis game</td> <td> 200</td> <td> 200</td> <td> Measured with Sonic 2</td> </tr> </tbody> </table> </div> <div> <h2>Game Cart Current Consumption</h2> <div>These values were measured on an NTSC Model 2 Genesis. These values are averages because the actual current consumption of cartridges is dynamic.</div> <div></div> <div> <table border="1" cellspacing="0"> <tbody> <tr> <td><b> Game</b></td> <td> <b>Avg (mA)</b></td> </tr> <tr> <td> Sonic The Hedgehog 3</td> <td> 13.2</td> </tr> <tr> <td> Sonic The Hedgehog 3 and Knuckles</td> <td> 11.9</td> </tr> <tr> <td> Super Street Fighter 2</td> <td> 19.1</td> </tr> <tr> <td> Virtua Racing</td> <td> 120.4</td> </tr> <tr> <td> Mega Everdrive</td> <td> 133.1 (160+ while loading)</td> </tr> <tr> <td> Power Base Mini + Double Dragon</td> <td> 6.9</td> </tr> <tr> <td> Power Base FM + Double Dragon</td> <td> 48.6</td> </tr> </tbody> </table> </div> <h2>Power Supply Connector Type</h2> </div> <div></div> <div> <table border="1" cellspacing="0"> <tbody> <tr> <td><b> Unit</b></td> <td><b> Connector Type</b></td> <td><b> Polarity</b></td> </tr> <tr> <td> Model 1 Genesis</td> <td> 2.1mm ID x 5.5mm OD</td> <td> Center negative</td> </tr> <tr> <td> Model 1 Sega CD</td> <td> 2.1mm ID x 5.5mm OD</td> <td> Center negative</td> </tr> <tr> <td> Model 2 Sega CD</td> <td> 2.1mm ID x 5.5mm OD</td> <td> Center negative</td> </tr> <tr> <td> Model 2 Genesis</td> <td> EIAJ-03 (1.7mm ID x 4.75mm OD)*</td> <td> Center positive</td> </tr> <tr> <td> 32X</td> <td> EIAJ-03 (1.7mm ID x 4.75mm OD)*</td> <td> Center positive</td> </tr> </tbody> </table> </div> *Some distributors will list the Model 2 Genesis and 32X power supply connector as 1.7mm ID x 4.8mm OD <h1>Schematics</h1> <h2>Model 1</h2> <ul> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vbmhKX2VLNWpTcnM/view?usp=drivesdk" title="genesis-1_block_diagram.png" icon="https://ssl.gstatic.com/docs/doclist/images/icon_11_image_list.png" newwindow="yes" plain="yes" style="normal"]</li> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vMTdBdjZiSDlSZGs/view?usp=drivesdk" title="genesis-1_cpu_and_custom_chips.png" icon="https://ssl.gstatic.com/docs/doclist/images/icon_11_image_list.png" newwindow="yes" plain="yes" style="normal"]</li> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vQy1YTFdDdmhmTTg/view?usp=drivesdk" title="genesis-1_sound_and_video.png" icon="https://ssl.gstatic.com/docs/doclist/images/icon_11_image_list.png" newwindow="yes" plain="yes" style="normal"]</li> </ul> <h2>Model 2 VA0</h2> <ul> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vLW1ZMXBveFJlX1U/view?usp=drivesdk" title="genesis-2-md-2-schematic-1_of_4.png" icon="https://ssl.gstatic.com/docs/doclist/images/icon_11_image_list.png" newwindow="yes" plain="yes" style="normal"]</li> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vejFRLXp1TUJjc00/view?usp=drivesdk" title="genesis-2-md-2-schematic-2_of_4.png" icon="https://ssl.gstatic.com/docs/doclist/images/icon_11_image_list.png" newwindow="yes" plain="yes" style="normal"]</li> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vX0p2VWl2SmM5WEE/view?usp=drivesdk" title="genesis-2-md-2-schematic-3_of_4.png" icon="https://ssl.gstatic.com/docs/doclist/images/icon_11_image_list.png" newwindow="yes" plain="yes" style="normal"]</li> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vZTM2Yjg4WlFOYXM/view?usp=drivesdk" title="genesis-2-md-2-schematic-4_of_4.png" icon="https://ssl.gstatic.com/docs/doclist/images/icon_11_image_list.png" newwindow="yes" plain="yes" style="normal"]</li> </ul> <h2>Model 2 VA1</h2> <ul> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vTGlpQnM3R1Nvekk/view?usp=drivesdk" title="genesis-2-md-2-schematic-va1-1_of_4.png" icon="https://ssl.gstatic.com/docs/doclist/images/icon_11_image_list.png" newwindow="yes" plain="yes" style="normal"]</li> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vWndXNGN4SWtwQzg/view?usp=drivesdk" title="genesis-2-md-2-schematic-va1-2_of_4.png" icon="https://ssl.gstatic.com/docs/doclist/images/icon_11_image_list.png" newwindow="yes" plain="yes" style="normal"]</li> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vcEVobUxlZ2ZfaVk/view?usp=drivesdk" title="genesis-2-md-2-schematic-va1-3_of_4.png" icon="https://ssl.gstatic.com/docs/doclist/images/icon_11_image_list.png" newwindow="yes" plain="yes" style="normal"]</li> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vZjUxcUtRajhJTGs/view?usp=drivesdk" title="genesis-2-md-2-schematic-va1-4_of_4.png" icon="https://ssl.gstatic.com/docs/doclist/images/icon_11_image_list.png" newwindow="yes" plain="yes" style="normal"]</li> </ul> <h1>Documents</h1> <ul> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vMHI5SnBTcmNtSFE/view?usp=drivesdk" title="sega_service_manual_-_genesis_ii_-_mega_drive_ii_pal-b-i-g_rgb_no_001_june_1993.pdf" icon="https://ssl.gstatic.com/docs/doclist/images/icon_12_pdf_list.png" newwindow="yes" plain="yes" style="normal"]</li> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vczBCb2syaUt0SjA/view?usp=drivesdk" title="sega_service_manual_supplement_-_genesis_ii_-_mega_drive_ii_pal-b-i-g_rgb_no_001-1_august_1993.pdf" icon="https://ssl.gstatic.com/docs/doclist/images/icon_12_pdf_list.png" newwindow="yes" plain="yes" style="normal"]</li> <li>[google-drive-embed url="https://drive.google.com/file/d/0BxWY40xxhh0vaWpjSUpVa0FleFE/view?usp=drivesdk" title="sega_service_manual_supplement_-_genesis_ii_-_mega_drive_ii_pal-b-i-g_rgb_no_001-2_december_1993.pdf" icon="https://ssl.gstatic.com/docs/doclist/images/icon_12_pdf_list.png" newwindow="yes" plain="yes" style="normal"]</li> </ul>
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February 13, 2017 @ 14:09:02 René
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René

Electronics engineer and retrogaming fanatic!