Expansion Port

The PC Engine Expansion Port

The PC Engine expansion includes pins for just about everything, including the entire cartridge port, RGB, audio, video, and a few other things. It also has access to the communications between the video chip and the CPU.

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Expansion Port Pinout

[[/images/PCEngineExpansionPort.png )

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23
C	SNDR	GND	HuD	CEK	A17	A13	A11	GND	D2	D4	D6	D7	A1	A3	A4	A6	GND	A15	A19	GND	Vout	Sync	Blu
B	SNDin	CDD	HSM	/WR	VU	A8	/OE	D0	D3	D5	HSn	A0	A2	VD6	A5	A7	A12	A16	A20	/RDY	IRQ2	/RST	Grn
A	SNDL	Vout	VS	A18	A14	A9	A10	D1	PCC	VSn	Vin	VD8	VD7	Vin	VD5	VD4	VD3	VD2	VD1	VD0	GND	Vid	Red
Power      Audio/Video      Data Bus      Address Bus      System Functions      Video Bus (?)

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The PC Shuttle Expansion Port

[[/images/PCShuttleExpansionPort.png ) The PC Engine Shuttle has a cut-down expansion connector. The primary change is the removal of the video bus pins and the IRQ2 pin, preventing the Shuttle from using a CD-ROM peripheral.

Shuttle Port Pinout

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
C	GND	Vout	A07	A04	A01	GND	D2	D5	GND	A10	A08	A17	GND	/OE	CDD	GND
B	GND	Vout	A12	A05	A02	GND	D1	D4	D7	A20	A09	A14	GND	HSM	Vout	GND
A	A19	A16	A15	A06	A03	A00	D0	D3	D6	GND	A11	A13	A18	/WR	Vout	/RST
Power      Data Bus      Address Bus      System Functions

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Label Explanations

Most of the functions in the PCE chart are active low.

System Functions

Label	Description
OE	Output Enable: Activates ROM chips and enables output.
CDD	CD Detect (aka K7 and Input Bit 7): Used for detecting the presence of a CD expansion unit.
HuD	HuCard Detect: Indicates the presence of a HuCard in the slot (cart port pin 1 is low).
HSM	High Speed Mode: Determines if the system runs at full speed (7.15909 MHz) or low speed (1.7897725 MHz).
RST	Reset: Resets the machine.
R/W	Read / Write: When set low, the data bus is in WRITE mode.
/RDY	Ready: No additional description provided.
IRQ2	Interrupt 2: Used to trigger events in the HuC6270.
A20	Often used as CE (Chip Enable). Activates ROM chips and enables output.

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Power

Label	Description
Vout	Voltage Out: +5V power supply for peripherals connected to the expansion port.
Vin	Voltage In: Sends power directly to the PC Engine, bypassing the power switch.

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Audio

Label	Description
SNDR	Sound Right: The right audio channel.
SNDL	Sound Left: The left audio channel.
SNDin	Sound Input: Single-channel audio input.

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Video Bus

Label	Description
HSn	Horizontal Sync: No additional description provided.
VSn	Vertical Sync: No additional description provided.
PCC	Pixel Clock: Possible values: 5.3693175 / 7.15909 / 10.738635 MHz.
VS	Unknown.
VU	Unknown.
VD0 - VD3	Video Bus Lines 0 - 3: Four-bit pixel value.
VD4 - VD7	Video Bus Lines 4 - 7: Four-bit palette value.
VD8	Video Bus Line 8: High for sprite/border pixels, low for background pixels.

Note: VD0 - VD8 are directly connected to the HuC6260 VCE.

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More information gathered from GameSX.com