SA9103C

sames

8/16

From the two bytes of data output by the device, the value for the register can

be derived as shown:

Register value =

(First Byte * 256) + Second Byte

The most significant bit of the 16 bit energy register (active or reactive) is an

indication of the direction of the energy flow (0 = positive, 1 = negative).

6.

Register Values

a.

The active and reactive energy measured per count, may be calculated by

applying the following formula:

Energy per Count

=

V * I

Watt seconds

K

Where

V

=

Rated Voltage

I

=

Rated Current

K

=

9281

for Active Energy

9281 * 2 for Reactive Energy

π

b.

The mains frequency may be calculated as follows:

Frequency

=

Crystal frequency

Register Value * 8

c.

To calculate the measured voltage, the following formula may be used:

Vmeasured =

V * n

14000 * t

Where

V

=

rated voltage

t

=

time difference between successive reads

n

=

difference in register values between

successive reads

The register access codes which can be written to the SA9103C via the serial

communications port are shown in the table below.

REGISTER

READ

RESET

READ-RESET

ACTIVE

$01

$02

$03

RE-ACTIVE

$81

$82

$83

VOLTAGE

$C1

$C2

$C3

FREQUENCY

$41

-

-

Data on SOUT

FIRST BYTE

DR-00835

8

9

10

11

12

13

14

15

SECOND BYTE

0

123

4

5

67