SunSaver MPPT MODBUS Document

TriStar MPPT MODBUS Document v10

http://www.morningstarcorp.com 25/26 05 Dec 2011

Examples

Read Holding Register, Scaling a voltage value

Read and scale the following value:

Variable (RAM): Battery Voltage

The voltage scaling term is stored in variable V_PU at addresses 0x0000 and 0x0001.

Suppose the following values are read from RAM:

Address Value(hex) Variable Name

0x0000 0x007B V_PU HI byte

0x0001 0xE041 V_PU LO byte

0x0018 0x0DB0 Battery Voltage value

1. Compute voltage scaler

Whole term = 0x007B  123

Fractional term = 0xE041 / 2^16  0.876

Voltage scaler = 123 + 0.876 = 123.876

Scaling for this variable is: n* V_PU * 2

-15

(as listed in the table of RAM variables)

2. Convert hexadecimal Vbattery register value to decimal

0x0DB0  3504

3. Scale Vbattery value

Vbattery = ( 3504 * 123.876 ) / 32768 = 13.25 Volts

Read Holding Register, 2 Word values

Variable (RAM): hours (hourmeter)

LO Register Address: 0x002A

HI Register Address: 0x002B

Scaling for this variable: none

1. read LO Register value(hex): 0x13D8

2. read HI Register value(hex): 0x0022

3. combine register values(hex): 0x002213D8

4. Convert to decimal: 2,233,304 hours