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AD7291

Rev. 0 | Page 19 of 28

Table 17. TSENSE Conversion Result Register (First Read)

MSB

D15

D14

D13

D12

D11

D10

ADD3

ADD2

ADD1

ADD0

B11

B10

Table 18. TSENSE Result Register (Second Read)

LSB

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

internal temperature sensor. See the Temperature Sensor

Averaging section for more details.

Table 19. TSENSE Average Result Register (First Read)

MSB

D15

D14

D13

D12

D11

D10

ADD3

ADD2

ADD1

ADD0

B11

B10

Table 20. TSENSE Average Result Register (Second Read)

LSB

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

B11

B10

Table 22. DATAHIGH Register (Second Read/Write)

LSB

DATALOW Register

The DATALOW register for each channel is a 16-bit read/write

Bit D12 are not used in the register and are set to 0s. The

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

B11

B10

Table 24. DATALOW Register (Second Read/Write)

LSB

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