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schematics:megadrive1bapinout [2019/08/27 20:45] (current)
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 +==== Bus Arbiter ===
  
 +The Bus Arbiter is just there to keep things clean and to stop processors treading on each other'​s toes. There'​s a fair few pins I've no idea what the function is for. Suggestions are welcome!
 +
 +^Pin^Name^Description^-^Pin^Name^Description^
 +|1|  GND  |Ground|-|51|MCLK|Master Clock input|
 +|2|  -  |Unknown|-|52| ​ -  |Unknown|
 +|3|  -  |Unknown|-|53| ​ -  |Unknown|
 +|4|  -  |Unknown|-|54| ​ -  |Unknown|
 +|5|  VA8  |68K Address 8|-|55| ​ -  |Unknown|
 +|6|  VA9  |68K Address 9|-|56| ​ !SOUND ​ |YM-2612 !CS|
 +|7|  VA10  |68K Address 10|-|57| ​ ZCLK  |Z80 clock|
 +|8|  VA11  |68K Address 11|-|58| !WRES  |Reset button input|
 +|9|  VA12  |68K Address 12|-|59| ​ !ZRAM  |Z80 memory !CE|
 +|10|  VA13  |68K Address 13|-|60| ​ !REF  |Unknown|
 +|11|  VA14  |68K Address 14|-|61| ​ !M1  |Z80 !M1|
 +|12|  VA15  |68K Address 15|-|62| ​ !ZRES  |Z80 Reset|
 +|13|  VA16  |68K Address 16|-|63| ​ !ZBR  |Z80 !BUSRQ|
 +|14|  VA17  |68K Address 17|-|64| ​ !WAIT  |Z80 !WAIT|
 +|15|  VA18  |68K Address 18|-|65| ​ !ZBAK  |Z80 !BUSAK|
 +|16|  VA19  |68K Address 19|-|66| !ZWR  |Z80 !WR|
 +|17|  VA20  |68K Address 20|-|67| ​ !ZRD  |Z80 !RD|
 +|18|  VA21  |68K Address 21|-|68| ​ !IREQ  |Z80 !IREQ|
 +|19|  VA22  |68K Address 22|-|69| ​ !MREQ  |Z80 !MREQ|
 +|20|  VA23  |68K Address 23|-|70| ​ !NMI  |Z80 !NMI|
 +|21|  FC0  |68K FC0|-|71| ​ ZA0  |Z80 Address 0|
 +|22|  FC1  |68K FC1|-|72| ​ ZA7  |Z80 Address 7|
 +|23|  !VPA  |68K !VPA|-|73| ​ ZA8  |Z80 Address 8|
 +|24|  !VRES  |68K !Reset|-|74| ​ ZA9  |Z80 Address 9|
 +|25|  !HALT  |68K !HALT|-|75| ​ ZA10  |Z80 Address 10|
 +|26|  VD8  |68K Data 8|-|76| ​ ZA11  |Z80 Address 11|
 +|27|  -  |Unknown|-|77| ​ -  |Unknown|
 +|28|  -  |Unknown|-|78| ​ -  |Unknown|
 +|29|  -  |Unknown|-|79| ​ -  |Unknown|
 +|30|  VCLK  |68K Clock|-|80| ​ ZA12  |Z80 Address 12|
 +|31|  GND  |Ground|-|81| ​ ZA13  |Z80 Address 13|
 +|32|  !TIME  |Unknown|-|82| ​ ZA14  |Z80 Address 14|
 +|33|  !CAS0  |I/O !CAS0|-|83| ​ ZA15  |Z80 Address 15|
 +|34|  !DTAK  |68K !DTAK|-|84| ​ ZD00  |Z80 Data 0|
 +|35|  R/!W  |68K R/​!W|-|85| ​ !FDWR  |Unknown|
 +|36|  !LDS  |68K !LDS|-|86| ​ -  |Unknown|
 +|37|  !VDS  |68K !UDS|-|87| ​ !ROM  |Unknown|
 +|38|  !AS  |68K !AS|-|88| ​ !ASEL  |Unknown|
 +|39|  !INTAK ​ |VDP !INTAK|-|89| ​ !CAS2  |Unknown|
 +|40|  -  |Unknown|-|90| ​ -  |Unknown|
 +|41|  !VDPM  |Unknown|-|91| ​ !RAS2  |VDP !RAS2|
 +|42|  !BG  |68K !BG|-|92| ​ !CE0  |Unknown|
 +|43|  !BGAK  |68K !BGACK|-|93| ​ !VTOV  |I/O !VTOV|
 +|44|  !BR  |68K !BR|-|94| ​ !ZTOV  |I/O !ZTOV|
 +|45|  !EOE  |68K memory 2 !OE|-|95| ​ !SRES  |I/O !SRES|
 +|46|  IA14  |Unknown|-|96| ​ !IO  |I/O !IO|
 +|47|  !NOE  |68K memory 1 !OE|-|97| ​ !M3  |I/O !M3|
 +|48|  EDCL  |HSCLK|-|98| ​ !CART  |Cartridge presence|
 +|49|  !OE0  |x|-|99| ​ -  |Unknown|
 +|50|  !HSYNC ​ |!HSYNC from VDP|-|100| ​ -  |Unknown|
 +
 +There'​s some supply pins that are marked as unknown, solely because I developed a headache whilst doing this!
 
 schematics/megadrive1bapinout.txt ยท Last modified: 2019/08/27 20:45 (external edit)
 
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