Industrial I/V Output Driver, Single-Supply, 55 V Maximum Supply. Industrial Current Out Driver, Single-Supply, 55 V Maximum Supply. Industrial Current/Voltage Output Driver with Programmable Ranges Quad Channel, 12-Bit, Serial Input, 4-20mA Output DAC with Dynamic Power. Quad-Channel, 12-Bit, Serial Input, 4 mA to 20 mA and Voltage Output DAC with. Authorġ6-Channel, 16-Bit, Serial Input, Voltage-Output DACġ6-Channel, 14-Bit, Serial Input, Voltage-Output DACĨ-Channel, 16-Bit, Serial Input, Voltage-Output DACĨ-Channel, 14-Bit, Serial Input, Voltage-Output DAC This method increases the reliability of data transfers and ensures that corrupted data is almost never accepted. When the data and checksum are sent to a compatible Analog Devices product, the data will be accepted only if both pieces of data arrive correctly. ![]() Applying the CRC-8 polynomial to the data generates a checksum of 0x86. The example shown in Figure 2 uses the (hex) value of 0圆54321 as a sample 24-bit data word. Generating a checksum for a 24-bit number (0圆54321). Figure 2 demonstrates how the checksum is developed. Eventually, the original data will be reduced to a value that is less than the CRC polynomial. (Numbers that match give Logic 0, nonmatches give Logic 1.) The CRC polynomial is again aligned so that its MSB is adjacent to the leftmost Logic 1 of the first result, and the procedure is repeated. An exclusive-or (XOR) function is applied to the data to produce a new (shorter) number. The CRC polynomial is aligned so that its MSB is adjacent to the leftmost Logic 1 of the 32-bit data. To generate the checksum, the 24-bit data is left-shifted by eight bits to create a 32-bit number ending in eight Logic 0s. For x = 2, this is equivalent to the binary value 100000111. The CRC-8 algorithm uses the polynomial C(x) = x 8 + x 2 + x 1 + 1. Temperature sensor hub and fan controller Industrial current/voltage output drivers with programmable rangesĤ-channel, 16-bit, 4-mA to 20-mA current- and voltage-output DACsĤ-channel, 16-bit, 4-mA to 20-mA current-output DACs Examples of Analog Devices Parts That Use Packet Error Checking Part Number SPI write with and without packet error checking. Table 1 lists a sample of Analog Devices parts that can use packet error checking. Figure 1 shows an example of how the data is applied using an SPI interface. The controller clears the error, returns the pin high, and resends the data. If the received checksum does not agree with the data, an output pin is brought low to indicate the error. To add the PEC function, the 24-bit data is augmented with a corresponding 8-bit checksum. 24-bit data is written when the PEC function is not required. Many Analog Devices DACs implement CRC in the form of a packet error check (PEC). Combining the checksum with the data, transmitting all 32 bits to a device that can analyze the combination, and indicating errors that occur-though not a totally perfect solution-is more efficient than the write-and-read method. CRC-8 produces an 8-bit checksum when applied to a 24-bit word. ![]() Checksums are commonly generated by applying a polynomial equation to the data. The receiving device will indicate if a problem has occurred, so the controller does not need to verify reception. ![]() This method is reliable, but it also comes with a large overhead: each piece of data must be verified, doubling the amount of data transferred.Īn alternative, cyclic redundancy checking (CRC), is to send a checksum with each packet of data. If the received data doesn't match the sent data, one of them has been corrupted-and new data must be sent and verified. The simplest is for the controller to read back the data that was sent. Several methods are available to ensure that the correct data has been received before action is taken. This could not only be dangerous but costly: imagine the arm smashing into the side of a new car on a production line-or, worse yet, into a production worker. For example, if the data sent to a DAC controlling the position of a robotic arm were corrupted, the arm could move in an unintended direction. Cyclic Redundancy Checking Ensures Correct Data CommunicationsĮlectronic systems operating in industrial environments must often endure temperature extremes, electrically noisy environments, or other harsh conditions-nevertheless, it is critical that they work correctly.
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