Chapter 12: Hardware Pinouts

This chapter covers pinout for the I/O ports and headers.

Port and Socket Listing

VERA Connectors
SNES Controller Ports (x2)
IEC Port
PS/2 Keyboard and mouse
Expansion Slots (x4 in Gen1)
User Port Header
ATX Power Supply
Front Panel

Chip sockets are not listed; pinouts are available on their respective data sheets.

Disclaimer

The instructions and information in this document are the best available information at the time of writing. This information is subject to change, and no warranty is implied. We are not liable for damage or injury caused by use or misuse of this information, including damage caused by inaccurate information. Interfacing and modifying your Commander X16 is done solely at your own risk.

If you attempt to upgrade your firmware and the process fails, one of our community members may be able to help. Please visit the forums or the Discord community, both of which can be reached through https://commanderx16.com.

SNES Ports

The computer contains two SNES style ports and will work with Super Nintendo compatible game pads. An on-board pin header is accessible to connect two additional SNES ports.

Pin #	Description	Wire Color
1	+5v	White
2	Data Clock	Yellow/Red
3	Data Latch	Orange
4	Serial Data	Red/Yellow
5	N/C	-
6	N/C	-
7	Ground	Brown

The Data Clock and Data Latch are generated by the computer and are shared across all SNES ports. The Serial Data line is unique per controller.

Thanks to Console Mods Wiki

IEC Port

The IEC port is a female 6 pin DIN 45322 connector. The pinout and specifications are the same as the Commodore 128 computer, with the required lines for Fast IEC, as used by the 1571 and 1581 diskette drives. 1541 drives are also compatible, using standard IEC mode at 400-600 bytes/sec.

Pin	Description	Signal Direction	Remark
1	SERIAL SRQ	IN	Serial Service Request In, at the C128 "Fast Serial Clock"
2	GND	-	Ground, signal ground (0V)
3	SERIAL ATN	OUT	Attention, for the selection of a device at beginning/end of a transmission
4	SERIAL CLK	IN/OUT	Clock (for data transmission)
5	SERIAL DATA	IN/OUT	Data
6	SERIAL RESET	OUT(/IN)	Reset

The IEC protocol is beyond the scope of this document. Please see Wikipedia for more information.

PS/2 Keyboard and Mouse

Pin	Name	Description
1	+DATA	Data
2	NC	Not connected
3	GND	Ground
4	Vcc	+5 VDC
5	+CLK	Clock
6	NC	Not Connected

Expansion Cards / Cartridges

The expansion slots can be used for I/O modules and RAM/ROM cartridges and expose the full CPU address and data bus, plus the ROM bank select lines, stereo audio, and 5 IO select lines.

The expansion/cartridge port is a 60-pin edge connector with 2.54mm pitch. Pin 1 is in the rear-left corner.

Desc	Pin		Pin	Desc
-12V	1	[ ]	2	+12V
GND	3	[ ]	4	+5V
AUDIO_L	5	[ ]	6	GND
AUDIO_R	7	[ ]	8	ROMB7
IO3	9	[ ]	10	ROMB0
IO4	11	[ ]	12	ROMB1
IO7	13	[ ]	14	ROMB6
IO5	15	[ ]	16	ROMB2
IO6	17	[ ]	18	ROMB5
RESB	19	[ ]	20	ROMB3
RDY	21	[ ]	22	ROMB4
IRQB	23	[ ]	24	PHI2
BE	25	[ ]	26	RWB
NMIB	27	[ ]	28	MLB
SYNC	29	[ ]	30	D0
A0	31	[ ]	32	D1
A1	33	[ ]	34	D2
A2	35	[ ]	36	D3
A3	37	[ ]	38	D4
A4	39	[ ]	40	D5
A5	41	[ ]	42	D6
A6	43	[ ]	44	D7
A7	45	[ ]	46	A15
A8	47	[ ]	48	A14
A9	49	[ ]	50	A13
A10	51	[ ]	52	A12
A11	53	[ ]	54	SDA
GND	55	[ ]	56	SCL
+5V	57	[ ]	58	GND
+12V	59	[ ]	60	-12V

To simplify address decoding, pins IO3-IO7 are active for specific, 32-byte memory mapped IO (MMIO) address ranges.

Address	Description
$9F60-$9FFF	Expansion port I/O range
$9F60-$9F7F	IO3
$9F80-$9F9F	IO4
$9FA0-$9FBF	IO5
$9FC0-$9FDF	IO6
$9FE0-$9FFF	IO7

Expansion cards can use the IO3-IO7 lines as enable lines to provide their IO address range(s), or decode the address from the address bus directly. To prevent conflicts with other devices, expansion boards should allow the user to select their desired I/O bank with jumpers or DIP switches.

ROMB0-ROMB7 are connected to the ROM bank latch at address $01. Values 0-31 ($00-$1F) address the on-board ROM chips, and 32-255 are intended for expansion ROM or RAM chips (typically used by cartridges, see below). This allows for a total of 3.5MB of address space in the $C000-$FFFF address range.

SCL and SDA pins are shared with the i2c connector on J9 and can be used to access i2c peripherals on cartridges or expansion cards.

AUDIO_L and AUDIO_R are routed to J10, the audio option header.

The other pins are connected to the system bus and directly to the 65C02 processor.

Cartridges

Cartridges are essentially an expansion card housed in an external enclosure. Typically they are used for applications (e.g. games) with the X16 being able to boot directly from a cartridge at power on. Typically they contain a mix of banked ROM and/or RAM and an optional I2C EEPROM (for storing game save states).

They can also function as an expansion card which means they can also use MMIO. Similarly an internal expansion card could contain RAM/ROM as well.

Because of this, while develoeprs are free to use the hardware as they please, there are open discussions on suggested best practices for using cartridges and expansion cards to avoid a poor user experience and or compatibility issues.

For example, there can be conflicts if an internal card uses RAM/ROM space allocated to cartridges. Similarly, a cartridge can use MMIO (and doing so allows for nice features such as accelerator co-processors), but care must be taken to avoid MMIO being used by internal cards.

One proposal is to reserve one of the MMIO address ranges for cartridges. These conversations are on-going such that the final best practices as well as the final cartridge and expansion card designs may change. To emphasize as well, these are neighborly best practices and not hard standards.

Booting from Cartridges

After the X16 finishes it's hardware initialization, the kernel checks bank 32 for the signature "CX16" at $C000. If found, it then jumps to $C004 and leaves interrupts disabled.

ATX Power Supply

The Commander X16 has a socket for an industry standard 24-pin ATX power supply connector. Either a 24-pin or 20-pin PSU connector can be plugged in, though only the pins for the older 20-pin standard are used by the computer. You don't need an expensive power supply, but it must supply the -12v rail. Not all do, so check your unit to make sure. If you can't tell from the label, you can check Pin 12 and COM. If the clip side is facing away from you, pin 14 will be the second pin on the left on the clip side. For a 20-pin cable, -12v is on pin 12, but at the same relative position — the second pin on the left on the clip side.

24-pin ATX power connector, cable end

By CalvinTheMan - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=50881708

The Commander X16 does not use the 4-pin CPU power, GPU power, 4-pin drive power, or SATA power connectors.

To save space, when running a bare motherboard, we recommend a "Pico PSU" power supply, which derives all of the necessary power lines from a single 12V source.

J1 ROM Write Protect

Remove J1 to write protect system ROM. With J1 installed, users can program the system ROM using an appropriate ROM flash program.

J2 NMI

Connect a button here to generate an Non Maskable Interrupt (NMI) on the CPU. This will execute a BASIC warm start, which will stop any existing program, clear the screen, and print the READY prompt.

J3 (Unknown)

Connect J8 for LPT Compat. (TODO: Is this the Centronics parallel port mode Lorin hinted at early on?)

J4 Extra 65C22 Pins

Desc	Pin		Pin	Desc
CA1	1	. .	2	CA2
PB0	3	. .	4	PB1
PB2	5	. .	6	CB2

These pins are connected to VIA 1 at $9F00-$9F0F.

J5 Program Microcontroller

Remove jumpers from J5 to program microcontroller.

J6 System Speed

Pin	Desc
1 - 2	8 MHz
3 - 4	4 MHz
5 - 6	2 MHz

J7 SNES 3/4

Desc	Pin		Pin	Desc
CLC	1	. .	2	VCC
LATCH	3	. .	4	DAT4
DAT3	5	. .	6	GND

These pins will allow for two additional SNES controllers, for a total of four controllers on the system.

J8 Front Panel

Desc	Pin		Pin	Desc
HDD LED+	1	. .	2	POW LED +
HDD LED-	3	. .	4	POW LED -
RESET BUT	5	. .	6	POW BUT
RESET BUT	7	. .	7	POW BUT
+5VDC	9	. .	10	NC

This pinout is compatible with newer ATX style motherboards. AT motherboards and older ATX cases may still have a 3-pin power LED connector (with a blank pin in the middle.) You will need to move the + (red) wire on the power LED connector to the center pin, if this is the case. Or you can use two Male-Female breadboard cables to jumper the header to your power LED connector.

There is no on-board speaker header. Instead, all audio is routed to the rear panel headphone jack via the Audio Option header.

J9 I2C/SMC Header

Desc	Pin		Pin	Desc
SMC MOSI/I2C SDA	1	. .	2	5V STANDBY
RTC MFP	3	. .	4	SMC TX
SMC Reset	5	. .	6	SMC RX
SMC SCK/I2C SCL	7	. .	8	GND
SMC MISO	9	. .	10	GND

J10 Audio Option

Desc	Pin		Pin	Desc
SDA	1	. .	2	RESB
SCL	3	. .	4	VCC
	5	. .	6
+12V	7	. .	8	-12V
	9	. .	10
VERA_L	11	. .	12	BUS_L
	13	. .	14
VERA_R	15	. .	16	BUS_R
	17	. .	18
YM_L	19	. .	20	OUT_L
	21	. .	22
YM_R	23	. .	24	OUT_R

5,6,9,10,13,14,17,18,21,22 - GND

Next to the audio header is a set of jumper pads, JP1-JP6. Cutting these traces allows you to extract isolated audio from each of the system devices or build a mixer to adjust the relative balance of the audio devices.

In order to avoid ground loop and power supply noise, we recommend installing a ground loop isolator when using an external mixer. 2 or 3 isolators will be required (one for each stereo pair.) (TODO: measure noise and test with pro audio gear.)

J12 User Port

Desc	Pin		Pin	Desc
PB0	1	. .	2	PB4
PA0	3	. .	4	PB5
PA1	5	. .	6	PB6/CB1
PA2	7	. .	8	PB7/CB2
PA3	9	. .	10	GND
PA4	11	. .	12	GND
PA5	13	. .	14	GND
PA6	15	. .	16	GND
PA7	17	. .	18	GND
CA1	19	. .	20	GND
PB1	21	. .	22	GND
PB2	23	. .	24	GND
PB3/CA2	25	. .	16	VCC

User port is connected to VIA 2 at address $9F10-$9F1F. This can be used for serial or parallel port I/O. Commander X16 does not have support for a serial port device in the KERNAL.

VERA Video Header

Desc	Pin		Pin	Desc
VCC	1	. .	2	GND
D7	3	. .	4	D6
D5	5	. .	6	D4
D3	7	. .	8	D2
D1	9	. .	10	D0
/IO1	11	. .	12	RESB
/MEMWE	13	. .	14	IRQB
A4	15	. .	16	/MEMOE
A2	17	. .	18	A3
A0	19	. .	20	A1
GND	21	. .	22	GND
VERA_L	23	. .	24	VERA_R

VERA is connected to I/O ports at $9F20-$9F3F. See VERA Programmer's Reference for details.

VGA Connector

Pin	Desc
1	RED
2	GREEN
3	BLUE
4
5	GND
6	RED_RTN
7	GREEN_RTN
8	BLUE_RTN
9
10	GND
11
12
13	HSync
14	VSync
15

The VGA connector is a female DE-15 jack.

The video resolution is 640x480 59.5FPS progressive scan, RGB color, and separated H/V sync.

In interlace mode, both horizontal and vertical sync pulses will appear on the HSync pin. (TODO: Test with OSSC).

VERA does not use the ID/DDC lines.

Composite Connector

The Composite video is a standard RCA connector. Center pin carries signal. Shield is signal ground.

The signal is NTSC Composite baseband video.

The video is 480 lines 59.97Hz interlaced. Composite is not available when VGA is running at 59.5Hz progressive scan.

S-Video Connector

Pin	Desc
1	GND (Y)
2	GND (C)
3	Y	Intensity (Luminance)
4	C	Color (Chrominance)

The connector is a 4-pin Mini-DIN connector. While the same size as a PS/2 connector, the PS/2 connector has a plastic key at the bottom. Do not attempt to plug a keyboard or mouse into the S-Video port, or bent pins will occur.

The signal is NTSC baseband Y/C separated video. S-Video provides better resolution than composite, since the color and intensity are provided on separate pins. you can use a splitter cable to separate the Y and C signals to drive a Commodore 1702 or compatible monitor.