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SUBJECT [Question] 8. What operational mode W3100A-LF support?
NAME WIZnet DATE 2007-05-29 HIT 2613
The W3100A-LF has three operational modes. They are distinguished according to the methods for adjusting MCU timing. All of them use 25MHz clock for W3100A-LF's internal operations.
1) 'Clocked mode' In 'Clocked mode', the same clock (25MHz) is used for adjusting timing between W3100A-LF and MCU. Basically we recommend you to use 'clocked mode' for this mode is the most stable and easiest one. But clocked mode is not suitable for the case in which MCU access time is shorter than 100ns.

2) 'External clocked mode' In 'External clocked mode', another clock is used for timing. If you use a clock faster than 25MHz, you'd better use 'external clocked mode'. CLOCK is used for timeout and EXT_CLK is used for MCU I/F. This is supported up to Maximum 75MHz. However, it could not be guaranteed at any faster clock than 75MHz.

3) 'Non-clocked mode' No clock is used for timing between the W3100A-LF and MCU. If CS, RD, and WR of your MCU satisfy W3100A-LF timing, you can use 'non-clocked mode'. CLOCK is used for timeout only. In case of Non-clocked mode, you should keep to the stated timing in Datasheet closely.

You can find the timing diagram in the W3100A datasheet.








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