MarketZX Interface 1
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ZX Interface 1

The ZX Interface 1, launched in 1983, was a peripheral from Sinclair Research for its ZX Spectrum home computer. Originally intended as a local area network interface for use in school classrooms, it was revised before launch to also act as the controller for up to eight ZX Microdrive high-speed tape-loop cartridge drives. It also included a DE-9 RS-232 interface capable of operating at up to 19.2 kbit/s. At hardware level it was fundamentally a voltage adaptor, the serial protocol being implemented in software by bit-banging. This led to problems when receiving data, but not when transmitting.

Network
peripheral ZX Interface 1 The device offered two network ports, allowing up to 64 ZX Spectrums to be daisy-chained using network leads up to long. The network, called ZX Net, used a bidirectional wire with a proprietary CSMA-like protocol. Data could be sent or received at either to or from a numbered workstation, or broadcast to all nodes, allowing one machine to act as a server. Station number 0 is used to indicate broadcast. Data is transmitted in packets, each a maximum of 255 bytes long; the packet and the header are protected by a checksum. Character transmission uses 1 start bit, 8 data bits and 1 stop bit (the common 8-N-1 configuration). Main commands: :FORMAT "n"; :SAVE * "n"; :LOAD * "n"; Select for example 1 as the address of the first computer (station number): :FORMAT "n";1 :SAVE * "n";2 Select 2 for the second computer address: :FORMAT "n";2 :LOAD * "n";1 Which will then transfer the program from "1" to "2". Other commands: :CAT # Lists the file and directory contents of unit # :LOAD * "m";1;"name" # Loads the program "name" from "microdrive" unit 1 The same protocol, renamed QLAN, was later used on the Sinclair QL. This was intended to be interoperable with ZX Net, but due to timing differences interoperability was found to be problematic. == See also ==
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