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Data Sheet
AD7291
Rev. B | Page 19 of 28
Table 17. TSENSE Conversion Result Register (First Read)
MSB
D15
D14
D13
D12
D11
D10
D9
D8
ADD3
ADD2
ADD1
ADD0
B11
B10
B9
B8
Table 18. TSENSE Result Register (Second Read)
LSB
D7
D6
D5
D4
D3
D2
D1
D0
B7
B6
B5
B4
B3
B2
B1
B0
TSENSE AVERAGE RESULT REGISTER (0x03)
The TSENSE average result register is a 16-bit read-only register
used to store the average result from the internal temperature
sensor. This register stores the average temperature readings
from the ADC in an 11-bit twos complement format, D11 to
D0, and uses Bit D15 to Bit D12 to store the channel address
bits. The TSENSE average result register is updated after every
TSENSE conversion is completed. The first TSENSE average
conversion result given by the AD7291 after averaging is
enabled is the actual first TSENSE conversion result. Table 13 details the temperature data format, which applies to the
Table 19. TSENSE Average Result Register (First Read)
MSB
D15
D14
D13
D12
D11
D10
D9
D8
ADD3
ADD2
ADD1
ADD0
B11
B10
B9
B8
Table 20. TSENSE Average Result Register (Second Read)
LSB
D7
D6
D5
D4
D3
D2
D1
D0
B7
B6
B5
B4
B3
B2
B1
B0
LIMIT REGISTERS (0x04 TO 0x1E)
The AD7291 has nine pairs of limit registers. Each pair stores
high and low conversion limits for each analog input channel
and the internal temperature sensor. Each pair of limit registers
has one associated hysteresis register. All 27 registers are 16 bits
wide; only the 12 LSBs of the registers are used for the AD7291.
The four MSBs, D15 and D12, in these registers should contain
0s. During power-up, the contents of the DATAHIGH register for
each analog voltage channel is full scale (0x0FFF), while the
default contents of the DATALOW voltage channels registers is
zero scale (0x0000). The output coding of the AD7291 is twos
complement for the temperature conversion result. The default
content for the TSENSE DATAHIGH register is 0x07FF, while the
default content of the TSENSE DATALOW register is 0x0800. The
AD7291 signals an alert in hardware if the conversion result
moves outside the upper or lower limit set by the limit registers.
DATAHIGH Register
The DATAHIGH registers for CH0 to CH7 and the internal
temperature sensor are 16-bit read/write registers; only the
12 LSBs of each register are used. Bit D15 to Bit D12 are not
used in the register and are set to 0s. This register stores the
upper limit that activates the ALERT output. If the value in the
conversion result register is greater than the value in the
DATAHIGH register, an ALERT occurs for that channel. When
the conversion result returns to a value at least N LSBs below
the DATAHIGH register value, the ALERT output pin is reset. The
value of N is taken from the hysteresis register associated with
that channel. The ALERT pin can also be reset by writing to
Bit D2 in the command register.
Table 21. DATAHIGH Register (First Read/Write)
MSB
D15
D14
D13
D12
D11
D10
D9
D8
0
B11
B10
B9
B8
Table 22. DATAHIGH Register (Second Read/Write)
LSB
D7
D6
D5
D4
D3
D2
D1
D0
B7
B6
B5
B4
B3
B2
B1
B0
DATALOW Register
The DATALOW register for each channel is a 16-bit read/write
register; only the 12 LSBs of each register are used. Bit D15 to
Bit D12 are not used in the register and are set to 0s. The
register stores the lower limit that activates the ALERT output.
If the value in the TSENSE conversion result register is less than
the value in the DATALOW register, an ALERT occurs for that
channel. When the conversion result returns to a value at least
N LSBs above the DATALOW register value, the ALERT output
pin is reset. The value of N is taken from the hysteresis register
associated with that channel. The ALERT output pin can also be
reset by writing to Bit D2 in the command register.
Table 23. DATALOW Register (First Read/Write)
MSB
D15
D14
D13
D12
D11
D10
D9
D8
0
B11
B10
B9
B8
Table 24. DATALOW Register (Second Read/Write)
LSB
D7
D6
D5
D4
D3
D2
D1
D0
B7
B6
B5
B4
B3
B2
B1
B0