How do I interpret register values in ADE7880?

Document created by hmani on Oct 3, 2014Last modified by hmani on Oct 3, 2014
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There are different types of registers in ADE7880 and here is a guide to help understand how to interpret values of some of the most commonly used regsiters:

 

24-bit signed registers- Sign extended to 28-bits and zero-padded to 32 bits (ZPSE)

The 24-bit signed value is sign-extended to 28-bits and zero padding is done at the end to extend it to 32-bits, as shown below.

 

ZPSE.png

 

Register value read back  (in hex)

Register value (in decimal)

FF9999A

-419430

28F5C

167772

Note: Use 2’scomplement form to convert into decimal format, when sign bit is 1.

 

24-bit signed registers- Sign extended to 32-bits (SE)

 

SE.png

 

Register value read back  (in hex)

Register value (in decimal)

7FFFFF

8388607

FFF00000

-1048576

Note: Use 2’scomplement form to convert into decimal format, when sign bit is 1.

 

Gain registers

24-bit signed value with MSB representing the sign. Sign-extended to 28 bits and zero padded to 32 bits.

 

Write to the IC

Read from the IC

Scale (in %)

Register (in decimal)

Register (in hex)

Register (in hex)

Register (in decimal)

Scale (in %)

-5

-419430

FF9999A

FF9999A

-419430

-4.999995232

25

2097152

200000

200000

2097152

25

 

Note: If -5% scaling is needed, then a decimal value of 223 * (-5%) must be provided to the register. Similarly, while reading back from the register, divide the register value by 223 to understand the scaling used.

 

Registers that come under this category:

Registers

Address locations

xxGAIN

0x4380-0x4386

xPGAIN

0x4389,0x438B, 0x438D, 0x4398

 

Power Factor

a) 16-bit signed register

The MSB is the sign bit. Each LSB has weight of 2-15. So, convert the register value into its decimal equivalent and multiply by 2-15, to get the power factor result.

 

Register value read back  (in hex)

Register value (in decimal)

Power Factor

7500

29952

0.9140625

F136

-3786

-0.115539551

 

Registers that come under this category:

Registers

Address locations

xPF

0xE902-0xE904

 

b) 24-bit signed register

MSB is sign bit. Sign-extended to 28 bits and zero padded to 32 bits. Each LSB has weight of 2-15. So, convert the register value into its decimal equivalent and multiply by 2-15, to get the power factor result.

 

Register value read back  (in hex)

Register value (in decimal)

Power Factor

FD9999A

-2516582

-0.299999952

5C28F6

6039798

0.720000029

 

Registers that come under this category:

Registers

Address locations

FPF

0xE885

HxPF

0xE88D,0xE895, 0xE89D

 

Harmonic distortion

These registers are in 3.21 signed format. The 3.21 signed format is a representation in which most significant three bits are assigned to the integer value of the decimal number. The less significant 21 bits constitute the fractional component. The most significant bit of the integer portion is the sign bit. Obtain the actual value of the register by dividing the register value by 221.

 

Register value read back  (in hex)

Register value (in decimal)

Harmonic distortion

7FFFFF

8388607

3.999999523

6FDE

28638

0.013655663

 

Registers that come under this category:

Registers

Address locations

xTHD

0xE886,0xE887

HxxHD

0xE88E,0xE88F,0xE896,0xE897,0xE89E,0xE89F

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