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EP20K400 データシート(PDF) 19 Page - Altera Corporation |
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EP20K400 データシート(HTML) 19 Page - Altera Corporation |
19 / 117 page Altera Corporation 19 APEX 20K Programmable Logic Device Family Data Sheet Normal Mode The normal mode is suitable for general logic applications, combinatorial functions, or wide decoding functions that can take advantage of a cascade chain. In normal mode, four data inputs from the LAB local interconnect and the carry-in are inputs to a four-input LUT. The Quartus II software Compiler automatically selects the carry-in or the DATA3 signal as one of the inputs to the LUT. The LUT output can be combined with the cascade-in signal to form a cascade chain through the cascade-out signal. LEs in normal mode support packed registers. Arithmetic Mode The arithmetic mode is ideal for implementing adders, accumulators, and comparators. An LE in arithmetic mode uses two 3-input LUTs. One LUT computes a three-input function; the other generates a carry output. As shown in Figure 8, the first LUT uses the carry-in signal and two data inputs from the LAB local interconnect to generate a combinatorial or registered output. For example, when implementing an adder, this output is the sum of three signals: DATA1, DATA2, and carry-in. The second LUT uses the same three signals to generate a carry-out signal, thereby creating a carry chain. The arithmetic mode also supports simultaneous use of the cascade chain. LEs in arithmetic mode can drive out registered and unregistered versions of the LUT output. The Quartus II software implements parameterized functions that use the arithmetic mode automatically where appropriate; the designer does not need to specify how the carry chain will be used. Counter Mode The counter mode offers clock enable, counter enable, synchronous up/down control, synchronous clear, and synchronous load options. The counter enable and synchronous up/down control signals are generated from the data inputs of the LAB local interconnect. The synchronous clear and synchronous load options are LAB-wide signals that affect all registers in the LAB. Consequently, if any of the LEs in an LAB use the counter mode, other LEs in that LAB must be used as part of the same counter or be used for a combinatorial function. The Quartus II software automatically places any registers that are not used by the counter into other LABs. |
同様の部品番号 - EP20K400 |
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同様の説明 - EP20K400 |
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