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In the beginning, available Ethernet controllers were large in pin count. Controllers originally designed for PC networks included 100 pin count devices from Realtek, SMSC, or Cirrus Logic. The ISA interface required by these controllers included 16 data lines, 5 address lines and 2 lines for read and write functions. Not only did this design increase the design complexity and occupied board space, in order to have reasonable functionality including analog for sensing or PWM channels, a large I/O, 80 pin host microcontroller was necessary. This next series of slides will walk through the approaches for adding Ethernet into embedded designs and how original challenges have been overcome. Available Ethernet controllers were large in pin count. Controllers originally designed for PC networks included 100 pin count devices from Realtek, SMSC, or Cirrus Logic. The ISA interface required by these controllers included 16 data lines, 5 address lines and 2 lines for read and write functions. Not only did this design increase the design complexity and occupied board space, but in order to have reasonable functionality including analog for sensing or PWM channels etc, a large I/O, 80 pin host microcontroller was necessary. Now at this point it must be mentioned that the connection to Ethernet through the RJ-45 connector requires the standard twisted pair for transmission or the TX+/TX- and also the twisted pair for receive or RX+ and RX-. This interface will remain constant through the next few slides.
