The TurboGrafx-16 HuCard (sold as the TurboChip in North America) uses a 38-pin PCB edge connector shared with the Japanese PC Engine. The card is credit-card-sized (approximately 85.6 mm × 54 mm, roughly 1.5 mm thick) and was introduced with the TurboGrafx-16 in North America in 1989. The bus is driven by the NEC/Hudson HuC6280 CPU, which provides a 21-bit post-MMU physical address bus (PA0–PA20) and an 8-bit bidirectional data bus (D0–D7) on a single +5 V supply. Although the physical connector is identical to the PC Engine version, the TurboGrafx-16 mainboard wires the data lines in descending order (D7 on pin 15 through D0 on pin 23), the reverse of the PC Engine arrangement; HuCards for each region are programmed accordingly, providing de-facto region lockout.
| Pin | Name | Description |
|---|---|---|
| 1 | ? | |
| 2 | ? | |
| 3 | A18? | Address 18 |
| 4 | A16 | Address 16 |
| 5 | A15 | Address 15 |
| 6 | A12 | Address 12 |
| 7 | A7 | Address 7 |
| 8 | A6 | Address 6 |
| 9 | A5 | Address 5 |
| 10 | A4 | Address 4 |
| 11 | A3 | Address 3 |
| 12 | A2 | Address 2 |
| 13 | A1 | Address 1 |
| 14 | A0 | Address 0 |
| 15 | D7 | Data 7 |
| 16 | D6 | Data 6 |
| 17 | D5 | Data 5 |
| 18 | GND | Ground |
| 19 | D4 | Data 4 |
| 20 | D3 | Data 3 |
| 21 | D2 | Data 2 |
| 22 | D1 | Data 1 |
| 23 | D0 | Data 0 |
| 24 | /CE | Chip Select |
| 25 | A10 | Address 10 |
| 26 | /OE | Output Enable |
| 27 | A11 | Address 11 |
| 28 | A9 | Address 9 |
| 29 | A8 | Address 8 |
| 30 | A13 | Address 13 |
| 31 | A14 | Address 14 |
| 32 | A17 | Address 17 |
| 33 | A19? | Address 19 |
| 34 | R/W | Read/Write |
| 35 | ? | |
| 36 | ? | |
| 37 | ? | |
| 38 | +5V | +5 VDC |
Notes
- Pin 1 is the short pin on the left (if the card is to inserted forwards)
- Pin 38 is the long pin on the right
- The 38-pin edge connector is a proprietary NEC/Hudson specification; no public manufacturer datasheet for the connector’s mechanical or electrical characteristics has been located.
- Address lines are presented in a non-sequential order on the connector (pins 3–14), matching standard 1-Mbit EPROM footprints.
- Pin 24 (/CE) carries PA20, the 21st address line from the HuC6280 CPU, which simultaneously serves as the active-low chip-enable for the ROM.
- The maximum addressable ROM capacity via the 21-bit address bus is 2 MB (16 Mbit); most HuCards were 512 KB–1 MB.
- The data bus (pins 15–23) is wired in descending order on the TurboGrafx-16 (D7…D0), the reverse of the PC Engine (D0…D7). The physical card and connector are otherwise identical across both regions.
Signals
- A0–A19 — Post-MMU CPU address lines (PA0–PA19) from the HuC6280, presented in a scrambled order across pins 3–14 and 25–33.
- /CE — Active-low chip-enable (pin 24); also carries PA20, the 21st post-MMU address line.
- D0–D7 — 8-bit bidirectional data bus; wired in descending order (D7 on pin 15, D0 on pin 23) on the TurboGrafx-16 mainboard.
- /OE — Output enable (read strobe) from the CPU to the cartridge ROM.
- R/W — Read/Write control line from the CPU.
- GND — Ground (pin 18).
- +5V — Single +5 V supply (pin 38).
- Pin 1 — function unknown.
- Pin 2 — function unknown.
- Pin 35 — function unknown.
- Pin 36 — function unknown.
- Pin 37 — function unknown.