Gast
#4741728
http://owfs-developers.narkive.com/AUIHTOAL/family-code-81 https://www.loxforum.com/forum/verkabelung-installation/11117-ds2401-mit-falscher-seriennummer-kein-ibutton Beitrag "1-Wire DS2438 mit Family Code A6?" unknown family code 81 wrong family code a6 Die Meldung kommt öfter, vor allem bei speziellen 1-wire-ICs und Quellen in China. http://www.chinaseniorsupplier.com/Security_Protection/Access_Control_Systems_Products/60051589056/Magnetic_Key_Ibutton_DS1990_Family_Code_81.html Die Erklärung findet sich im Book of iButton Standards: http://pdfserv.maximintegrated.com/en/an/AN937.pdf Seite 12: C.1 . Family Code The family code is a type-specific value that references the device's functionality and capacity. The lower seven bits of the family code indicate the device type; the most significant bit of the family code is used to flag custom- er-specific versions. Thus 128 different standard devices can be coded. .... If the most significant bit of the family code is set, the device's functionality is still the same as that of the stan- dard device, but the serial number follows special rules. C.3. Special Rules for Customer Codes If the custom flag of the family code is set, a part of the number pool is reserved to designate specific custom- ers. That is, the 12 most significant bits of the serial number allow 4096 different customers each to have their own special device. The code for these 12 bits is assigned by Dallas Semiconductor with the first cus- tomer order. Since the ROM section is 64 bits, and 8 bits are taken each for family code and CRC, there remain 36 bits to store customer-defined data together with unique serial numbers. Customer-specific devices require special registration and ordering procedures to control access to only one customer. Customer-spe- cific devices can be made public if officially authorized by the originator. Depending on their requirements, customers have four options for using the remaining 36 ROM bits. Option A allows the eight most significant bits of this range to be programmed with customer-defined data, leaving 28 bits for unique serial numbers (268.4 million combina- tions). Option B allows the 1 2 most significant bits to be customer-defined, still allowing 16.8 million unique serial numbers. With Option C, the customer can spec- ify the 1 6 most significant bits; the pool of unique serial numbers, however, diminishes to 1 .05 million. Option D allows the 20 most significant bits to be defined by the customer, but the total number of unique serial numbers reduces to just 65,536. A more complete description of customer-specific devices is available on request. .... Um es richtig zu machen, muss man das Bit7 wegmaskieren, also mit 0x7f andieren, bevor man den Family-Code auswertet. Folgende ICs habe ich schon gesehen:
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