The Genesis/Megadrive contained a relatively powerful display processor (for the time), otherwise known as the VDP. This occupied position IC-8 on the circuit board, and is numbered 315-5313.
| Pin | Name | Description | - | Pin | Name | Description |
|---|---|---|---|---|---|---|
| 1 | SD0 | Display RAM Data 0 | - | 65 | CD10 | 68K Data 10 |
| 2 | SD1 | Display RAM Data 1 | - | 66 | CD11 | 68K Data 11 |
| 3 | SD1 | Display RAM Data 2 | - | 67 | CD12 | 68K Data 12 |
| 4 | SD1 | Display RAM Data 3 | - | 68 | CD13 | 68K Data 13 |
| 5 | SD1 | Display RAM Data 4 | - | 69 | CD14 | 68K Data 14 |
| 6 | SD1 | Display RAM Data 5 | - | 70 | CD15 | 68K Data 15 |
| 7 | SD1 | Display RAM Data 6 | - | 71 | CA0 | 68K Address 1 |
| 8 | SD1 | Display RAM Data 7 | - | 72 | CA1 | 68K Address 2 |
| 9 | - | Unknown | - | 73 | CA2 | 68K Address 3 |
| 10 | !SE 0 | Display RAM !SOE | - | 74 | CA3 | 68K Address 4 |
| 11 | SC | Display RAM SC | - | 75 | CA4 | 68K Address 5 |
| 12 | !RAS | Display RAM !RAS | - | 76 | CA5 | 68K Address 6 |
| 13 | !CAS | Display RAM !CAS | - | 77 | CA6 | 68K Address 7 |
| 14 | - | Unknown | - | 78 | CA7 | 68K Address 8 |
| 15 | !WE | Display RAM !WE | - | 79 | CA8 | 68K Address 9 |
| 16 | !OE 1 | Display RAM !DT/!OE | - | 80 | CA9 | 68K Address 10 |
| 17 | GND | Ground | - | 81 | CA10 | 68K Address 11 |
| 18 | - | Unknown | - | 82 | CA11 | 68K Address 12 |
| 19 | - | Unknown | - | 83 | CA12 | 68K Address 13 |
| 20 | - | Unknown | - | 84 | CA13 | 68K Address 14 |
| 21 | - | Unknown | - | 85 | CA14 | 68K Address 15 |
| 22 | - | Unknown | - | 86 | CA15 | 68K Address 16 |
| 23 | - | Unknown | - | 87 | CA16 | 68K Address 17 |
| 24 | - | Unknown | - | 88 | CA17 | 68K Address 18 |
| 25 | - | Unknown | - | 89 | CA18 | 68K Address 19 |
| 26 | AGC | Analog Ground | - | 90 | CA19 | 68K Address 20 |
| 27 | R | Red output | - | 91 | CA20 | 68K Address 21 |
| 28 | G | Green output | - | 92 | CA21 | 68K Address 22 |
| 29 | B | Blue output | - | 93 | CA22 | 68K Address 23 |
| 30 | AVC | Analog video supply voltage | - | 94 | AVS | Analog sound supply voltage |
| 31 | AD0 | Display RAM Address 0 | - | 95 | PSG | PSG Sound output |
| 32 | AVC | Display RAM Address 1 | - | 96 | AGS | Analog sound ground |
| 33 | AVC | Display RAM Address 2 | - | 97 | GND | Ground |
| 34 | AVC | Display RAM Address 3 | - | 98 | !INT | Z80 Interrupt |
| 35 | AVC | Display RAM Address 4 | - | 99 | !BR | 68K !BR |
| 36 | AVC | Display RAM Address 5 | - | 100 | !BGAK | 68K !BGACK |
| 37 | AVC | Display RAM Address 6 | - | 101 | !BG | 68K !BG |
| 38 | AVC | Display RAM Address 7 | - | 102 | !MRE0 | Bus Arbiter !VDPN |
| 39 | !YS | Video? | - | 103 | !BG | 68K !BG |
| 40 | SPA/B | Pulled up to VCC1 | - | 104 | !IPL1 | 68K !IPL1 (Interrupt) |
| 41 | !VSYNC | VSync to Bus Arbiter | - | 105 | !IPL2 | 68K !IPL2 (Interrupt) |
| 42 | !C-SYNC | Composite Sync to encoder | - | 106 | !IREQ | Z80 IREQ |
| 43 | !HSYNC | HSync to Bus Arbiter | - | 107 | !RD | Z80 !RD |
| 44 | !HL | 68K Halt? | - | 108 | !WR | Z80 !WR |
| 45 | SEL0 | !M3 | - | 109 | !MI | Z80 !MI |
| 46 | !PAL | NTSC flag input | - | 110 | !AS | 68K !AS |
| 47 | !RESET | !SRES | - | 111 | !UDS | 68K !UDS |
| 48 | SELI | Pulled down to GND | - | 112 | !LDS | 68K !LDS |
| 49 | !CLKI | 68K Clock out | - | 113 | R/!W | 68K Read/!Write |
| 50 | SBCR | SBCR (X in) | - | 114 | !DTAK | 68K !DTACK |
| 51 | CLK0 | Z80 Clock out | - | 115 | !UWR | 68K memory !UWR |
| 52 | MCLK | Master Clock in | - | 116 | !LWR | 68K memory !LWR |
| 53 | EDCK | HS_CLK in | - | 117 | !OE0 | 68K memory !OE0 |
| 54 | VDD | VCC1 | - | 118 | !CAS0 | 68K memory !CAS0 |
| 55 | CD0 | 68K Data 0 | - | 119 | !RAS0 | 68K memory !RAS0 |
| 56 | CD1 | 68K Data 1 | - | 120 | - | Unknown |
| 57 | CD2 | 68K Data 2 | - | 121 | - | Unknown |
| 58 | CD3 | 68K Data 3 | - | 122 | - | Unknown |
| 59 | CD4 | 68K Data 4 | - | 123 | - | Unknown |
| 60 | CD5 | 68K Data 5 | - | 124 | - | Unknown |
| 61 | CD6 | 68K Data 6 | - | 125 | - | Unknown |
| 62 | CD7 | 68K Data 7 | - | 126 | - | Unknown |
| 63 | CD8 | 68K Data 8 | - | 127 | - | Unknown |
| 64 | CD9 | 68K Data 9 | - | 128 | VDD | VCC1 |
Note:
Oddities with the way that memory is connected to the VDP means that the local V-RAM chips are split across a dedicated data bus and a shared data/address bus. I'm not sure why this is!