Vaisala HUMICAP MMT162 Guía de usuario descargar pdf (Pagina 46)

User's Guide _______________________________________________________________________

44 ___________________________________________________________________ M210934EN-D

Modbus Communication

The Modbus variant used in MMT162 communication is Modbus RTU.

Below is an example of a request to read the currently measured

temperature value from transmitter with address 240, and the response

from the transmitter.

Request to read registers 3 and 4 (currently measured value of T):

F0h

03h

00h

02h

00h

02h

70h

EAh

transmitter

address

function

code

address of

first register

number of

registers to

read

CRC check

Response as IEEE 754-2008 binary32 (41BBA77Ch = 23.4568 °C):

F0h

03h

04h

A7h

7Ch

41h

BBh

88h

73h

transmitter

address

function

code

number of

data bytes to

data from

first register

data from

second

CRC check

For a list of available Modbus registers, see Appendix A Modbus

Reference on page 70.

Accessing Serial Port Command Interface from

Modbus Mode

You cannot change configuration settings (other than Modbus address)

while the device is in the Modbus mode. To use the configuration

commands on a Modbus-enabled device:

1. Connect the USB service cable to the PC and install the driver, if

necessary.

2. Open the terminal program and open a connection to the

corresponding COM port using settings 19200, 8, N, 1, no flow

control.

3. Plug the service cable to the connector II of the instrument.

4. In less than three seconds, send a hash character (#) and carriage

return (Enter) to the device using the terminal program. The device

is now ready for configuration commands. The Modbus mode is

restored on next power-up unless Modbus is disabled with

command SMODE.

For example, if you want to deactivate the Modbus mode on a MMT162

device, follow the procedure above and deactivate the Modbus mode

with command SMODE STOP. On subsequent power-ups, the serial

command interface will be activated.

1 2 ... 41 42 43 44 45 46 47 48 49 50 51 ... 74 75

Comentarios a estos manuales

Sin comentarios

Vaisala HUMICAP MMT162 Guía de usuario Pagina 46

Comentarios a estos manuales

Relacionado con productos y manuales para De medición, control y control Vaisala HUMICAP MMT162