Datasheet ADT7461A (ON Semiconductor) - 9

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ADT7461A
for both internal and external results. Temperature values are register on the ADT7461A that is stored in the address offset by 64°C in the offset binary data format. Examples of pointer register. It is to this register address that the second temperatures in both data formats are shown in Table 8. byte of a write operation is written, or to which a subsequent read operation is performed.
Table 8. TEMPERATURE DATA FORMAT
The power-on default value of the address pointer register
(TEMPERATURE HIGH BYTE)
is 0x00. Therefore, if a read operation is performed
Offset Binary
immediately after power-on, without first writing to the
Temperature Binary
(Note 1) address pointer, the value of the local temperature is returned –55°C 0 000 0000 0 000 1001 because its register address is 0x00. (Note 2)
Temperature Value Registers
0°C 0 000 0000 0 100 0000 The ADT7461A has three registers to store the results of +1°C 0 000 0001 0 100 0001 local and remote temperature measurements. These +10°C 0 000 1010 0 100 1010 registers can only be written to by the ADC and can be read +25°C 0 001 1001 0 101 1001 by the user over the SMBus. The local temperature value +50°C 0 011 0010 0 111 0010 register is at Address 0x00. +75°C 0 100 1011 1 000 1011 The external temperature value high byte register is at +100°C 0 110 0100 1 010 0100 Address 0x01, with the low byte register at Address 0x10. The power-on default for all three registers is 0x00. +125°C 0 111 1101 1 011 1101 +127°C 0 111 1111 1 011 1111
Configuration Register
+150°C 0 111 1111 1 101 0110 The configuration register is Address 0x03 at read and (Note 3) Address 0x09 at write. Its power-on default is 0x00. Only 1. Offset binary scale temperature values are offset by 64°C. four bits of the configuration register are used. Bit 0, Bit 1, 2. Binary scale temperature measurement returns 0°C for all Bit 3, and Bit 4 are reserved; the user does not write to them. temperatures < 0°C. 3. Binary scale temperature measurement returns 127°C for all Bit 7 of the configuration register masks the ALERT temperatures > 127°C. output. If Bit 7 is 0, the ALERT output is enabled. This is the The user can switch between measurement ranges at any power-on default. If Bit 7 is set to 1, the ALERT output is time. Switching the range likewise switches the data format. disabled. This applies only if Pin 6 is configured as ALERT. The next temperature result following the switching is If Pin 6 is configured as THERM2, then the value of Bit 7 reported back to the register in the new format. However, the has no effect. contents of the limit registers do not change. It is up to the If Bit 6 is set to 0, which is power-on default, the device user to ensure that when the data format changes, the limit is in operating mode with ADC converting. If Bit 6 is set to registers are reprogrammed as necessary. More information 1, the device is in standby mode and the ADC does not on this is found in the Limit Registers section. convert. The SMBus does, however, remain active in standby mode; therefore, values can be read from or written
ADT7461A Registers
to the ADT7461A via the SMBus. The ALERT and THERM The ADT7461A contains 22, 8-bit registers in total. These outputs are also active in standby mode. Changes made to registers store the results of remote and local temperature the registers in standby mode that affect the THERM or measurements, high and low temperature limits, and ALERT outputs cause these signals to be updated. configure and control the device. See the Address Pointer Bit 5 determines the configuration of Pin 6 on the Register section through the Consecutive ALERT Register ADT7461A. If Bit 5 is 0 (default), then Pin 6 is configured section of this data sheet for more information on the as an ALERT output. If Bit 5 is 1, then Pin 6 is configured ADT7461A registers. Additional details are shown in as a THERM2 output. Bit 7, the ALERT mask bit, is only Table 9 through Table 13. The entire register map is active when Pin 6 is configured as an ALERT output. If available in Table 14. Pin 6 is set up as a THERM2 output, then Bit 7 has no effect. Bit 2 sets the temperature measurement range. If Bit 2 is
Address Pointer Register
0 (default value), the temperature measurement range is set The address pointer register itself does not have, nor does between 0°C to +127°C. Setting Bit 2 to 1 sets the it require, an address because the first byte of every write measurement range to the extended temperature range operation is automatically written to this register. The data (−64°C to +191°C). in this first byte always contains the address of another
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