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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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MCRF250 датащи(PDF) 11 Page - Microchip Technology |
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MCRF250 датащи(HTML) 11 Page - Microchip Technology |
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11 / 24 page  2003 Microchip Technology Inc. DS21267F-page 11 MCRF250 5.0 ANTI-COLLISION The anti-collision feature is enabled after the array lock bit (CB12) is set. This feature relies on internal random number oscillator/counter and special gap pulses (= turn off RF field) provided by a reader. Figure 5-1 shows the anti-collision flowchart. The MCRF250 works with the following anti-collision features: 1. The device does not output data until it sees the first gap. (no RF field for about 60 µsec.) 2. When the device sees the first gap, the internal random number oscillator starts clocking immediately after the gap. 3. At the same time, the internal random number counter starts counting the random number clocks. 4. The device waits for 5 bit times (about 5 msec. for MOD128 configuration). Example: 1 bit time=RF/128=1 msec for 128 kHz for MOD128 5. After the 5 bit times, the device sends data. 6. At this time, the random number counter is still running. If multiple tags in the field send data at the same time, the reader will see a data collision. 7. When the reader sees the data collision, it sends the second gap pulse. (no RF field for about 60 µsec.) 8. After the second gap pulse, there is a chance that the random number counter of each tag may have a different value due to a random variation in the oscillator’s starting time, etc. 9. After the second gap, the random number oscillator stops and the random number counter will decrement at each subsequent gap. 10. The device will transmit data when its random number counter reaches ‘0’. 11. The device repeats this sequence (as shown in the flowchart in Figure 5-1) according to the proper gap pulses provided by the reader. FIGURE 5-1: ANTI-COLLISION FLOWCHART Note: Each device will output data in different time frames since each random number counter will arrive at ‘0’ at different times. As a result, the reader can receive clean data from a different tag in each time frame. Begin Provide Gap* Wait 5-bit times Is Read Tag Is only one tag modulating? modulation present? Provide gap in the first half of the first bit time to make tag stop transmitting No No Yes Yes Note: *Gap = lack of RF carrier signal = 60 µs ± 20%. |
Аналогичный номер детали - MCRF250 |
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Аналогичное описание - MCRF250 |
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