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AD7417BR Fiches technique(PDF) 14 Page - Analog Devices |
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AD7417BR Fiches technique(HTML) 14 Page - Analog Devices |
14 / 24 page AD7416/AD7417/AD7418 Rev. I | Page 14 of 24 ANALOG INPUT 0V 1/2LSB 111...111 111...110 111...000 011...111 000...010 000...001 000...000 +VREF – 1LSB 1LSB – VREF/1024 Figure 14. Ideal Transfer Function Characteristic for the AD7417/AD7418 Config2 Register (Address 0x05) A second configuration register is included in the AD7417/ AD7418 for the functionality of the CONVST pin. It is an 8-bit register with Bit D5 to Bit D0 being left at 0. Bit D7 determines whether the AD7417/AD7418 should be operated in its default mode (D7 = 0), performing conversions every 355 μs or in its CONVST pin mode (D7 = 1), where conversions start only when the CONVST pin is used. Bit 6 contains the Test 1 bit. When this bit is 0, the I2C filters are enabled (default). Setting this bit to 1 disables the filters. Table 16. Config2 Register D7 D6 D5 D4 D3 D2 D1 D0 Conversion mode Test 1 0 0 0 0 0 0 SERIAL BUS INTERFACE Control of the AD7416/AD7417/AD7418 is carried out via the I2C compatible serial bus. The AD7416/AD7417/AD7418 are connected to this bus as a slave device, under the control of a master device, for example, the processor. Serial Bus Address As with all I2C compatible devices, the AD7416/AD7417/AD7418 have a 7-bit serial address. The four MSBs of this address for the AD7416 are set to 1001; the AD7417 are set to 0101, and the three LSBs can be set by the user by connecting the A2 to A0 pins to either VDD or GND. By giving them different addresses, up to eight AD7416/AD7417 devices can be connected to a single serial bus, or the addresses can be set to avoid conflicts with other devices on the bus. The four MSBs of this address for the AD7418 are set to 0101, and the three LSBs are all set to 0. If a serial communication occurs during a conversion operation, the conversion stops and restarts after the communication. The serial bus protocol operates as follows: 1. The master initiates data transfer by establishing a start condi- tion, defined as a high-to-low transition on the serial data line, SDA, while the serial clock line, SCL, remains high. This indicates that an address/data stream follows. All slave peripherals connected to the serial bus respond to the 7-bit address (MSB first) plus an R/W bit, which determines the direction of the data transfer, that is, whether data is written to or read from the slave device. The peripheral whose address corresponds to the transmitted address responds by pulling the data line low during the low period before the ninth clock pulse, known as the acknowl- edge bit. All other devices on the bus now remain idle while the selected device waits for data to be read from or written to it. If the R/W bit is a 0, then the master writes to the slave device. If the R/W bit is a 1, then the master reads from the slave device. 2. Data is sent over the serial bus in sequences of nine clock pulses, eight bits of data followed by an acknowledge bit from the receiver of data. Transitions on the data line must occur during the low period of the clock signal and remain stable during the high period, because a low-to-high transi- tion when the clock is high may be interpreted as a stop signal. 3. When all data bytes have been read or written, stop conditions are established. In write mode, the master pulls the data line high during the 10th clock pulse to assert a stop condition. In read mode, the master device pulls the data line high during the low period before the ninth clock pulse. This is known as no acknowledge. The master then takes the data line low during the low period before the 10th clock pulse, then high during the 10th clock pulse to assert a stop condition. Any number of bytes of data can be transferred over the serial bus in one operation, but it is not possible to mix read and write in one operation because the type of operation is determined at the beginning and cannot subsequently be changed without starting a new operation. Writing to the AD7416/AD7417/AD7418 Depending on the register being written to, there are three different writes for the AD7416/AD7417/AD7418. • Writing to the address pointer register for a subsequent read. To read data from a particular register, the address pointer register must contain the address of that register. If it does not, the correct address must be written to the address pointer register by performing a single-byte write operation, as shown in Figure 15. The write operation consists of the serial bus address followed by the address pointer byte. No data is written to any of the data registers. • Writing a single byte of data to the configuration register, the Config2 register, or to the TOTI setpoint or THYST setpoint registers. The configuration register is an 8-bit register, so only one byte of data can be written to it. If only 8-bit temperature comparisons are required, the temperature LSB can be ignored in TOTI and THYST, and only eight bits need to be written to the TOTI setpoint and THYST setpoint registers. Writing a single byte of data to one of these registers consists of the serial bus address, the data register address written to the address pointer register, followed by the data byte |
Numéro de pièce similaire - AD7417BR |
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Description similaire - AD7417BR |
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