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The SPI slave protocol
For using the Netzer as Ethernet modem from i.e. another microcontroller there is a dedicated Netzer project “SPISlave”. This project implements an SPI slave mode. TCP/IP connections can be established and released (as client or server) and data can be received and sent.
Since version 1.4 the protocol and interface has significantly changed compared with prior versions. For older versions please check out the Elektor website.
Physical connection
At least six free pins on the master side are needed. See figure 1 diagramm for a typical connection.
All SPI pins are read only for the GPIO access (GPIO webpage). Other pins can be used as digital in or ouputs as needed.
Fig. 1:
Connection example
Fig. 2:
Waveforms
