Integrated Circuit Chips
There are several different types of chips used in NerdConsole.
Processor
RAM
System RAM in NerdConsole should operate at 55ns or faster.
ROM
Cartridge ROM in NerdConsole should operate at 150ns or faster.
- Chip - AT28C64 8KB ROM
- Chip - AT28C256 32KB ROM
- Chip - W27C512 64KB ROM
- Chip - SST39SF010 128KB ROM
- Chip - SST39SF020 256KB ROM
- Chip - SST39SF040 512KB ROM
Audio
Logic
- Chip - 74HCT00 4x 2-Input NAND
- Chip - 74HCT08 4x 2-Input AND
- Chip - 74HCT14 6x Inverter
- Chip - 74HCT30 1x 8-Input NAND
- Chip - 74HCT32 4x 2-Input OR
- Chip - 74HCT139 2x 2 to 4 Line Decoder
- Chip - 74HCT238 1x 3 to 8 Line Decoder
- Chip - 74HCT240 8x Inverting Buffer
- Chip - 74HCT273 8x D-Type Flip-Flops
Clock
STILL MOVING CHIP PINOUTS TO THEIR OWN PAGES
Audio
The audio system in NerdConsole has a dedicated audio processor which is driven the CPU. The output of that is then piped to the Raspberry Pi based PPU for inclusion in the HDMI signal.
YM-3812
The Yamaha YM-3812 is the same audio processor that was found in countless Adlib and SoundBlaster sound cards.
| VCC | 1 | 24 | M |
|---|---|---|---|
| ~IRQ | 2 | 23 | SY |
| ~IC | 3 | 22 | NC |
| A0 | 4 | 21 | MO |
| ~WR | 5 | 20 | SH |
| ~RD | 6 | 19 | NC |
| ~CS | 7 | 18 | D7 |
| NC | 8 | 17 | D6 |
| NC | 9 | 16 | D5 |
| D0 | 10 | 15 | D4 |
| D1 | 11 | 14 | D3 |
| GND | 12 | 13 | D2 |
YM-3014
This chip is a digital to analog converter (DAC) and is used to convert the digital signals produced by the YM-3812 into actual analog audio waveforms.
| VCC | 1 | 8 | MP |
|---|---|---|---|
| To BUFF | 2 | 7 | RB |
| LOAD | 3 | 6 | GND |
| SD | 4 | 5 | CLOCK |
Logic
NerdConsole uses a variety of logic chips for address decoding, holding register values, and buffering data as it moves between systems.
74HCT00
This chip provides four 2-input NAND gates.
| 1A | 1 | 14 | VCC |
|---|---|---|---|
| 1B | 2 | 13 | 4B |
| 1Y | 3 | 12 | 4A |
| 2A | 4 | 11 | 4Y |
| 2B | 5 | 10 | 3B |
| 2Y | 6 | 9 | 3A |
| GND | 7 | 8 | 3Y |
74HCT08
This chip provides four 2-input AND gates.
| 1A | 1 | 14 | VCC |
|---|---|---|---|
| 1B | 2 | 13 | 4B |
| 1Y | 3 | 12 | 4A |
| 2A | 4 | 11 | 4Y |
| 2B | 5 | 10 | 3B |
| 2Y | 6 | 9 | 3A |
| GND | 7 | 8 | 3Y |
74HCT14
This chip provides six signal inverters.
| 1A | 1 | 14 | VCC |
|---|---|---|---|
| 1Y | 2 | 13 | 6A |
| 2A | 3 | 12 | 6Y |
| 2Y | 4 | 11 | 5A |
| 3A | 5 | 10 | 5Y |
| 3Y | 6 | 9 | 4A |
| GND | 7 | 8 | 4Y |
74HCT30
This chip provides a single 8-input NAND gate. This is used to identify when extended RAM bank 255 is selected and thus extended RAM writes should instead be directed to the PPU.
| A | 1 | 14 | VCC |
|---|---|---|---|
| B | 2 | 13 | NC |
| C | 3 | 12 | H |
| D | 4 | 11 | G |
| E | 5 | 10 | NC |
| F | 6 | 9 | NC |
| GND | 7 | 8 | Y |
74HCT32
This chip provides four 2-input OR gates.
| 1A | 1 | 14 | VCC |
|---|---|---|---|
| 1B | 2 | 13 | 4B |
| 1Y | 3 | 12 | 4A |
| 2A | 4 | 11 | 4Y |
| 2B | 5 | 10 | 3B |
| 2Y | 6 | 9 | 3A |
| GND | 7 | 8 | 3Y |
74HCT139
This chip is provides 2 separate 2 to 4 line decoders. Each takes 2 inputs as a 2-bit number (0-3) and turns on the single line that corresponds to that number as output.
| ~1G | 1 | 16 | VCC |
|---|---|---|---|
| 1A | 2 | 15 | ~2G |
| 1B | 3 | 14 | 2A |
| 1Y0 | 4 | 13 | 2B |
| 1Y1 | 5 | 12 | 2Y0 |
| 1Y2 | 6 | 11 | 2Y1 |
| 1Y3 | 7 | 10 | 2Y2 |
| GND | 8 | 9 | 2Y3 |
74HCT238
This chip is a 3 to 8 line decoder. It takes 3 inputs as a 3-bit number (0-7) and turns on the single line that corresponds to that number as output.
| A0 | 1 | 16 | VCC |
|---|---|---|---|
| A1 | 2 | 15 | Y0 |
| A2 | 3 | 14 | Y1 |
| ~G0 | 4 | 13 | Y2 |
| ~G1 | 5 | 12 | Y3 |
| G2 | 6 | 11 | Y4 |
| Y7 | 7 | 10 | Y5 |
| GND | 8 | 9 | Y6 |
74HCT240
This chip reads the state of all 8 possible controllers and inverts the signal turning the 0s from pressed buttons into 1s.
| ~1OE | 1 | 20 | VCC |
|---|---|---|---|
| 1A0 | 2 | 19 | ~2OE |
| ~2Y3 | 3 | 18 | ~1Y0 |
| 1A1 | 4 | 17 | 2A3 |
| ~2Y2 | 5 | 16 | ~1Y1 |
| 1A2 | 6 | 15 | 2A2 |
| ~2Y1 | 7 | 14 | ~1Y2 |
| 1A3 | 8 | 13 | 2A1 |
| ~2Y0 | 9 | 12 | ~1Y3 |
| GND | 10 | 11 | 2A0 |
74HCT273
This chip provides an octal D-type flip-flops with a clear pin for ensuring a known state upon system reset. These are commonly used for holding upper address pin values for bank selection.
| ~CLR | 1 | 20 | VCC |
|---|---|---|---|
| 1Q | 2 | 19 | 8Q |
| 1D | 3 | 18 | 8D |
| 2D | 4 | 17 | 7D |
| 2Q | 5 | 16 | 7Q |
| 3Q | 6 | 15 | 6Q |
| 3D | 7 | 14 | 6D |
| 4D | 8 | 13 | 5D |
| 4Q | 9 | 12 | 5Q |
| GND | 10 | 11 | CLK |
Clock
Clock generation is handled with crystal oscillators. Regardless of the size (DIP-8 or DIP-14) the pinout is the same.
| NC | 1 | 4 | VCC |
|---|---|---|---|
| GND | 2 | 3 | Clock |
CPU Clock
The main CPU in NerdConsole operates at 6.00 MHz.
Audio Clock
The audio system in NerdConsole operates at 3.58 MHz. There is an independent clock crystal for this instead of doing clock division of the main CPU clock which would be less accurate and difficult.
