Datasheet ADT7461 (ON Semiconductor) - 9

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ADT7461 Table 7. TEMPERATURE DATA FORMAT
registers can only be written to by the ADC and can be read
(LOCAL AND REMOTE TEMPERATURE HIGH BYTE)
by the user over the SMBus. The local temperature value register is at Address 0x00.
Offset Binary
The external temperature value high byte register is at
Temperature Binary
(Note 1) Address 0x01, with the low byte register at Address 0x10. –55°C 0 000 0000 0 000 1001 The power-on default for all three registers is 0x00. (Note 2) 0°C 0 000 0000 0 100 0000
Configuration Register
+1°C 0 000 0001 0 100 0001 The configuration register is Address 0x03 at read and +10°C 0 000 1010 0 100 1010 Address 0x09 at write. Its power-on default is 0x00. Only four bits of the configuration register are used. Bits 0, 1, 3, +25°C 0 001 1001 0 101 1001 and 4 are reserved and should not be written to by the user. +50°C 0 011 0010 0 111 0010 Bit 7 of the configuration register is used to mask the +75°C 0 100 1011 1 000 1011 ALERT output. If Bit 7 is 0, the ALERT output is enabled. +100°C 0 110 0100 1 010 0100 This is the power-on default. If Bit 7 is set to 1, the ALERT +125°C 0 111 1101 1 011 1101 output is disabled. This only applies if Pin 6 is configured as +127°C 0 111 1111 1 011 1111 ALERT. If Pin 6 is configured as THERM2, the value of +150°C 0 111 1111 1 101 0110 Bit 7 has no effect. (Note 3) If Bit 6 is set to 0 (the power-on default), the device is in 1. Offset binary scale temperature values are offset by 64°C. operating mode with the ADC converting. If Bit 6 is set to 2. Binary scale temperature measurement returns 0°C for all 1, the device is in standby mode and the ADC does not temperatures < 0°C. 3. Binary scale temperature measurement returns 127°C for all convert. The SMBus does, however, remain active in temperatures > 127°C. standby mode, so values can be read from or written to the ADT7461 via the SMBus in this mode. The ALERT and The user can switch between measurement ranges at any THERM outputs are also active in standby mode. Changes time. Switching the range also switches the data format. The made to the registers in standby mode that affect the next temperature result following the switching is reported THERM or ALERT outputs cause these signals to be back to the register in the new format. However, the updated. contents of the limit registers are not changed. The user must Bit 5 determines the configuration of Pin 6 on the ensure that the limit registers are reprogrammed, as ADT7461. If Bit 5 is 0 (default), then Pin 6 is configured as necessary, when the data format changes. See the Limit an ALERT output. If Bit 5 is 1, then Pin 6 is configured as Registers section for more information. a THERM2 output. Bit 7, the ALERT mask bit, is only
ADT7461 Registers
active when Pin 6 is configured as an ALERT output. If The ADT7461 contains a total of 22 8-bit registers. These Pin 6 is set up as a THERM2 output, then Bit 7 has no effect. registers are used to store the results of remote and local Bit 2 sets the temperature measurement range. If Bit 2 is temperature measurements and high and low temperature 0 (default), the temperature measurement range is set limits and to configure and control the device. A description between 0°C to +127°C. Setting Bit 2 to 1 means that the of these registers follows. Additional details are provided in measurement range is set to the extended temperature range. Table 8 to Table 12.
Table 8. CONFIGURATION REGISTER BIT Address Pointer Register ASSIGNMENTS
The address pointer register does not have or require an
Power-On
address, as the first byte of every write operation is
Bit Name Function Default
automatically written to this register. The data in this first 7 MASK1 0 = ALERT Enabled 0 byte always contains the address of another register on the 1 = ALERT Masked ADT7461, which is stored in the address pointer register. 6 RUN/STOP 0 = Run 0 This register address is written to by the second byte of a 1 = Standby write operation or is used for a subsequent read operation. 5 ALERT/ 0 = ALERT 0 The power-on default value of the address pointer register THERM2 1 = THERM2 is 0x00. Therefore, if a read operation is performed 4, 3 Reserved 0 immediately after power-on, without first writing to the 2 Temperature 0 = 0°C to 127°C 0 address pointer, the value of the local temperature is Range Select 1 = Extended Range returned, since its register address is 0x00. 1, 0 Reserved 0
Temperature Value Registers
The ADT7461 has three registers to store the results of local and remote temperature measurements. These
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