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QD3512REVA Datasheet NOTES: 1. All VDD pins must be connected t0 2.5V power supply. 2. All VDDO pins must be connected to appropriate power supply: 3.3V if OPT pin for that port is set to VDD (2.5V) and 2.5V if OPT pin for that port is set to Vss (OV). 3. All Vss pins must be connected to ground. 4. A17x is a NC for IDT70T659. 5. Package body is approximately 28mm x 28mm x 3.5mm. 6. This package code is used to reference the package diagram. 7. 8ns Commercial and 10ns Industrial speed grades are not available in the DR-208 package. 8. This text does not indicate orientation of the actual part-marking. QD3512REVA Price Each DS1921 contains a unique ROM code that is 64 bits long. The first eight bits are a l-Wire family code. The next 36 bits are a unique serial number. The next 12 bits, called temperature range code, allow distinguishing the DS1921H and DS19212 from each other and from the various DS1921L-F5 versions. The last eight bits are a CRC of the first 56 bits. See Figure 3 for details. The l-Wire CRC is generated using a polynomial generator consisting of a shift register and XOR gates as shown in Figure 4. The polynomial is X8 + X5 + X4 + 1. Additional information about the Dallas l-Wire Cyclic Redundancy Check is available in Application Note 27 and in the Book of DS19xx iButton Standards. QD3512REVA on stock
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