WRT54GLSept12 - Embedded XINU and WRT54GL 1 Topics Logic...

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10/27/11 1 Embedded XINU and WRT54GL
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10/27/11 2 Topics Logic and shift operators Optimizing operations (mul, div VS shiftL, shiftR) WRT54GL architecture and internals Embedded XINU
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10/27/11 3 Shift Operators << left shift >> right shift Usage: unsigned int x = 70707; //x = 00000000 00000001 00010100 00110011 unsigned int y, z; y = x << 2; // y = 00000000 00000100 01010000 11001100 z = x >> 2; //z = 00000000 00000000 01000101 00001100
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10/27/11 4 Logic Operators Bitwise & (AND) Bitwise inclusive | (OR) Bitwise exclusive ^ (XOR) Bitwise negation ~ Usage: unsigned exp1 = 1; unsigned exp2 = 4; printf (“ %d\n”, exp1 | exp2); printf (“ %d\n”, exp1 & exp2); printf (“ %d\n”, exp1 ^ exp2); printf (“ %d\n”, ~exp1);
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10/27/11 5 Relevance of shift and logic operators Bitwise operations are necessary for much low-level programming, such as writing device drivers, low-level graphics, communications protocol packet assembly and decoding. Device drivers use these operators to test the presence or absence of a bit in a serial port or a device input. (checking for on or off)
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WRT54GL History of WRT54G Open source firmware Common features Processor architecture (BCM5352) WRT54GL Block diagram
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History Introduced in 2002 In 2003 Andrew Miklas posted to Linux Kernel Mailing List about Linksys using GPL code in its firmware Linksys executives gave into the pressure from the community, Linksys released the code to the community under GPL.
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Common Features Power: 12VDC 1.0amp This power requirement is standard for embedded devices and wireless access points This makes them compatible with Power over
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