ZX Interface 1

The ZX Interface 1 is a communications and storage interface for the ZX Spectrum released by Sinclair.

It provided an RS-232 serial interface, as well as storage using Microdrives and networking capabilities through the Sinclair Network, a proprietary interface of Sinclair's. The Sinclair Network would later be supported by MGT's DISCiPLE interface.

Port		Bit
		7	6	5	4	3	2	1	0
0xf7	Read	TX Data							Net Input
	Write								Net Output / RX Data
0xef	Read				Busy	DTR	Gap	Sync	Write Protect
	Write			Wait	CTS	Erase	R/W	Comms Clock	Comms Data
0xe7	Read	Microdrive data read
	Write	Microdrive data write

• TX Data is the value received by the serial port.
• Net Input is the value read from the Sinclair Network port.
• Bit 0 of port 0x7f is output to the serial port if Comms Data is set, or to the network port if Comms Data is reset.
• DTR signals that the remote station wishes to send data, CTS signals that the Spectrum wishes to send data
• Wait is used for network synchronisation.

• When Erase is reset the tape is erased and data is written, when set data is read.
• R/W instructs the microdrive to read or write. When R/W is set the microdrive runs, when reset it stops
• Comms Data is the value to be shifted into the microdrive select flip-flop chain.
• Comms Clock shifts the microdrive select bit along the chain.
• Write Protect is raised when a writeable cartridge is present in the selected microdrive.
• Gap and Sync are used to locate the correct block of data on the microdrive.