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LM75ADP データシート(PDF) 8 Page - NXP Semiconductors |
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LM75ADP データシート(HTML) 8 Page - NXP Semiconductors |
8 / 18 page Philips Semiconductors Product data sheet LM75A Digital temperature sensor and thermal Watchdog ™ 2004 Oct 05 8 I2C serial interface The LM75A can be connected to a compatible 2-wire serial interface I2C-bus as a slave device under the control of a controller or master device, using two device terminals, SCL and SDA. The controller must provide the SCL clock signal and write/read data to/from the device through the SDA terminal. Notice that if the I2C common pull-up resistors have not been installed as required for I2C-bus, then an external pull-up resistor, about 10 k Ω, is needed for each of these two terminals. The bus communication protocols are described in the data communication section. Slave address The LM75A slave address on the I2C-bus is partially defined by the logic applied to the device address pins A2, A1 and A0. Each of them is typically connected either to GND for logic 0, or to VCC for logic 1. These pins represent the three LSB bits of the device 7-bit address. The other four MSB bits of the address data are preset to ‘1001’ by hard wiring inside the LM75A. Table 1 shows the device’s complete address and indicates that up to 8 devices can be connected to the same bus without address conflict. Because the input pins, SCL, SDA, A2–A0, are not internally biased, it is important that they should not be left floating in any application. Table 1. Address table 1 = HIGH, 0 = LOW MSB LSB 1 0 0 1 A2 A1 A0 Register list The LM75A contains four data registers beside the pointer register as listed in Table 2. The pointer value, read/write capability and default content at power up of the registers are also shown in the Register table. Table 2. Register table Register name Pointer value R/W POR state Description Conf 01H R/W 00H Configuration Register. Contains a single 8-bit data byte. To set the device operating condition. Default = 0. Temp 00H Read only N/A Temperature Register. Contains two 8-bit data bytes. To store the measured Temp data. Tos 03H R/W 50 00H Over-temp Shutdown threshold Register. Contains two 8-bit data bytes. To store the over-temp shut-down Tos limit. Default = 80 °C. Thyst 02H R/W 4B 00H Hysteresis Register. Contains two 8-bit data bytes. To store the hysteresis Thyst limit. Default = 75 °C. Pointer register The pointer register contains an 8-bit data byte of which the two LSB bits represent the pointer value of the other four registers, and the other 6 MSB bits are equal to 0, as shown in the Pointer register table (Table 3) and the Pointer value table (Table 4). The pointer register is not accessible to the user, but is used to select the data register for write/read operation by including the pointer data byte in the bus command. Table 3. Pointer register table B7 B6 B5 B4 B3 B2 B1 B0 0 0 0 0 0 0 Pointer value Table 4. Pointer value B1 B0 Selected register 0 0 Temperature register (Temp) 0 1 Configuration register (Conf) 1 0 Hysteresis register (Thyst) 1 1 Overtemp shut-down register (Tos) Because the Pointer value is latched into the Pointer register when the bus command, which includes the pointer byte, is executed, a read from the LM75A may or may not include the pointer byte in the statement. To read again a register, which has been recently read and the pointer has been preset, the pointer byte does not have to be included. To read a register, which is different with the one that has been recently read, the pointer byte must be included. However, a write to the LM75A must always include the pointer byte in the statement. The bus communication protocols are described in detail in the data communication section. At power-up, the Pointer value is equal to 0 and the Temp register is selected; users can then read the Temp data without specifying the pointer byte. |
同様の部品番号 - LM75ADP |
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同様の説明 - LM75ADP |
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