CDi_MiSTer/doc/snac.md

SNAC (Serial Native Accessory Converter)

The User port of the MiSTer offers 7 data lines to use for the core. The serial port of the CD-i - at the front or back - makes use of 8 pins. 6 of those are data lines. Together with one line for the infrared signal for the remote controller, this seems to be a match.

Since every CD-i has different types of ports, we rely on the common denominator. Two SNAC modes are offered.

The RS232 Mode simulates a back port of a 210/05. It is connected to the UART of the SCC68070.

The Dual Input Mode simulates the front port of a CD-i that supports the official input port splitter.

• Without a splitter, it can take one pointing device which is connected to the SLAVE.
• With the splitter, the second device is connected to the SCC68070

	Dual Input Mode	RS232 Mode	Direction
1	RXD1	-	In
2	RXD2	RXD	In
3	TXD2	TXD	Out
4	RTS1	DTR	Out
5	GND	GND
6	-	CTS	In
7	RTS2	RTS	Out
8	+5V	+5V
9	RC-Eye	RC-Eye	In
	Can take 2 controllers using a splitter	Fully compatible to back Port