Connectors
Every socket, plug and header on the ACE, and what is on each pin. Read off the schematic rather than off the board, so it is right even where the silkscreen is crowded.
Round the outside
| What | Connector | Where it goes |
|---|---|---|
| Power | 5 V barrel jack | 5 V DC, 2–3 A. Center positive |
| Video | VGA | Any monitor that takes VGA. 640 × 480 |
| Audio L / R | Two RCA jacks | Powered speakers, or a hi-fi input |
| Serial | DB-9 male | A laptop, through a null-modem cable |
| Joystick A / B | Two DB-9 male | Atari 2600-compatible sticks |
| PS/2 | 6-pin mini-DIN | A PS/2 keyboard, working alongside the board's own |
| CompactFlash | On the CF adapter board | Your files |
| Cartridge | 2 × 20 card edge, standing up behind the keyboard | Cartridges, and the KIM keypad boards |
| Bus | 2 × 20 box header | The whole 65C02 bus, for anything you build |
There are four small jumper headers as well — PHI2 SELECT for the CPU speed, CTS EN and DCD EN for the serial handshake lines, and one that brings the reset switch out to a panel-mounted button. Those are build-time decisions, not things to plug into.
Joystick — DB-9
Both ports are wired the same way, port A to the VIA's port A and port B to its port B.
| Pin | Port A | Port B | Direction |
|---|---|---|---|
| 1 | PA4 | PB4 | Up |
| 2 | PA5 | PB5 | Down |
| 3 | PA6 | PB6 | Left |
| 4 | PA7 | PB7 | Right |
| 5 | PA3 | PB3 | Y |
| 6 | PA0 | PB0 | A / fire |
| 7 | PA1 | PB1 | B |
| 8 | GND | GND | Ground |
| 9 | PA2 | PB2 | X |
It reads backwards
A direction being held pulls its line to 0. An untouched stick reads 255 — every bit high. So the test is
IF (JOY(1) AND 16) = 0 THEN PRINT "UP"and not <> 0. This trips everyone once. Sticks and keys has the full bit table.
Serial — DB-9
The ACE is wired as data terminal equipment, the same as a PC. Two DTE ends both transmit on pin 3 and listen on pin 2, which means they talk past each other — so reaching a laptop needs a null-modem cable or adapter, not a straight-through one.
| Pin | Signal | Direction |
|---|---|---|
| 1 | DCD | In — carrier detect |
| 2 | RXD | In — the ACE receives here |
| 3 | TXD | Out — the ACE transmits here |
| 4 | DTR | Out |
| 5 | GND | Ground |
| 6 | DSR | In |
| 7 | RTS | Out |
| 8 | CTS | In |
| 9 | — | Not connected |
19200 baud, 8 data bits, no parity, one stop bit. Serial and a terminal covers what to do once it is plugged in.
PS/2 — 6-pin mini-DIN
| Pin | Signal |
|---|---|
| 1 | PS2DATA |
| 2 | Not connected |
| 3 | GND |
| 4 | VCC |
| 5 | PS2CLK |
| 6 | Not connected |
A keyboard here works alongside the board's own keys rather than instead of them — both end up in the same buffer, and you can type on either without switching anything.
The bus, and the cartridge edge
The bus header and the cartridge card edge carry exactly the same forty signals in the same order: the whole 65C02 bus, brought out twice. Odd pins down one side, even pins down the other.
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | GND | 2 | VCC |
| 3 | RESB | 4 | EXP0 |
| 5 | IRQB | 6 | EXP1 |
| 7 | NMIB | 8 | A15 |
| 9 | RDY | 10 | A14 |
| 11 | BE | 12 | A13 |
| 13 | RWB | 14 | A12 |
| 15 | SYNC | 16 | A11 |
| 17 | PHI2 | 18 | A10 |
| 19 | EXP3 | 20 | A9 |
| 21 | EXP2 | 22 | A8 |
| 23 | D7 | 24 | A7 |
| 25 | D6 | 26 | A6 |
| 27 | D5 | 28 | A5 |
| 29 | D4 | 30 | A4 |
| 31 | D3 | 32 | A3 |
| 33 | D2 | 34 | A2 |
| 35 | D1 | 36 | A1 |
| 37 | D0 | 38 | A0 |
| 39 | VCC | 40 | GND |
Two of the four expansion pins are spoken for
The family bus reserves EXP0 to EXP3. On the ACE, EXP0 and EXP1 are both tied to the hard-reset line — so a card designed against a COB backplane, expecting all four to be free, will not behave here.
GPIO — port A and port B
Two 2 × 6 box headers bring the 65C22 VIA's ports out, ten signals each.
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | VCC | 2 | GND |
| 3 | PA7 | 4 | PA0 |
| 5 | PA6 | 6 | PA1 |
| 7 | PA5 | 8 | PA2 |
| 9 | PA4 | 10 | PA3 |
| 11 | CA1 | 12 | CA2 |
Port B's header is the same with PB0–PB7, CB1 and CB2.
These are the same sixteen lines the keyboard matrix and the two joysticks use. Anything you hang here takes turns with them — see The keyboard and the sticks for the handshake.
Two internal headers
Keyboard — a 1 × 16 header at 2 mm pitch: pins 1–8 are PA0–PA7 (the matrix rows), pins 9–16 are PB0–PB7 (the columns). On a stock ACE the board's own switches are soldered across it. The keyboard matrix has the grid.
Storage — a 2 × 10 socket carrying eight data lines, three address lines, a read strobe, a write strobe and one chip select. That chip select is I/O slot 4, which is why the CompactFlash card appears at $8C00. The CF adapter board is nothing more than this header wired to a CF socket.
📄 Connectors card — every pinout on two printable pages, for the bench.