Contemporary Control Systems Modbus Cube I/O MR-AO4 User Manual

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7. Bit rate and Parity setting

The bit rate and parity can be set in the programming mode when

ajumper is plugged behind the front cover of the module. This

jumper is removed in normal mode. A connection to the bus is

not required during bit rate setting.
The bit rate of the modules can be set in the following way:
1. remove the front cover of the module;
2. plug a jumper to the two middle pins of the 4 pole header

between the red and green LED (Á);

3. set the desired parity and bit rate with the address switches

(Â) in accordance to the chart below.

4. switch on the supply voltage of the module; it is now per-

manently saving the bit rate in an EEPROM;

5. switch off the supply voltage of the module;
6. remove the jumper from the header and place the front

cover.

If the settings differ from the settings specified in the chart the

factory setting applies.
Factory setting: 19200 Bd Even

24V

ERROR

B +

MR-AO4

B+

+24V

GND

+24V

GND

BUSY

MODBus RTU

x10

Jumper below
the faceplate

6. Mounting

Power down the equipment

Mount the module on standard rail (TH35 per IEC 60715 in

junction boxes and/or on distribution panels).
Installation
Electric installation and device termination shall be done by

qualified persons only, by respecting all applicable

specifications and regulations.

Plug in the terminal block for bus connection

5 mm

The module can be aligned without interspace. Use the jumper

plug to connect bus and supply voltage when the modules are

mounted in series.
The maximum quantity of modules connected in line is limi-

ted to 15 or to a maximum power consumption of 2 Amps

(AC or DC) per connection to the power supply. For any

similar block of additional modules a separate connection

to the power supply is mandatory.

Connect the cable for bus supply

Mounting in series

Switch

Bitrate

(Bit/s) 1200 2400 4800 9600 19200 38400 57600 115200

Switch

x10

Parity even odd none

9. Software description

9.1 I/O Commands

“03 (0x03) Read Holding Registers”
Holding Register 0-3:

Output values of the outputs

Signed Integer16,

Holding Register 4-7:

Basic settings

of the output values

Request

Valid Register Starting Address 0..7 or 66
Valid Quantity of Registers

1..8 or 1

Response
Byte Count

2 x Quantity of Registers

Values Register 0..7

0x0000 to 0xFFFF

(0x7FFF = 10,24 Volt )

Einheit = 10,24V / 215 = 1V / 3200 = 0,3125 mV
Value Register 66
Time constant for communication monitoring.

monitoring, all other values are for communication monitoring

with a solution of 10 ms.
0x0000 to 0xFFFF => 0 to 655,35 seconds = 10,9 minutes
“06 (0x06) Write Single Register”
Request

Valid Register Address

0..7 or 66

Valid Value Register 0..7

0x0000 to 0xFFFF

(0x7FFF = 10,24 Volt )

Valid Value Register 66

0x0000 to 0xFFFF

(0 to 655,35 seconds )

Response

Echo of the request

“16 (0x10) Write Multiple Registers”
Request

Valid Register Starting Address 0..7
Valid Quantity of Registers

1..8

Valid Byte Count

2 x Quantity of Registers (QoR)

Valid Value Register 0..7

QoR x 0x0000 to 0xFFFF

(0x7FFF = 10,24 Volt )

Response

Function Code, Register Starting Address, Quantity of Registers

9.2 Bit rate setting with Modbus command

Parity and bit rate have the same value as when setting them by

address switch.
If Parity or Bit has the value 0, no setting or storage is carried

out.
The register content is stored in the EEPROM.

Continuation Software description

“06 (0x06) Write Single Register”
Request
Valid Register Address

0x41 ( 65 )

Valid Register Value 2 Bytes

Bit 15-8: Magic-Number 0x53 = 83 as protection against

accidental

writing.

The command will be further analysed only with this

number.

Response

Echo of Request

Example for a frame:

Slave address

0x12 Setting of rotary switch (18)

Function

0x06 Write Single Register

0x00

0x41 Bit rate and parity (65)

All devices can be switched simultaneously with a Broadcast com-

mand (Slave address 0x00) However, it is advised not to do so as

this can cause problems:

- Devices from other manufacturers may have under this

address a register for a different purpose that will then be

operated in the wrong way.
- There is no feedback from the individual devices.

Consequently the control cannot immediately recognize if

the command was correctly received.

It is safer to address and switch each device individually.
The device will then answer with the old settings of parity and

bit rate. Switching will take place only afterwards. However, the

answer can get lost if the bus is disturbed.
When all devices are switched; it is advised to check communica-

tion. Any function of the device providing a feedback is suitable.

If a single function is to be used being independent from the

process periphery then the function „Diagnostic“ sub-function

„Return Query Data“ is suitable, it returns the transferred data.
If bit rate and parity setting of a device are unknown it is possible

to address the device successively with all combinations of bit

rate and parity until the device answers. Try the most likely com-
binations first. Try the lower bit rates last as they take longer.

15 14 13 12 11 10 9

0x53

Parity

Bit rate

Bit 3-0

Bit rate 1200 2400 4800 9600 19200 38400 57600 115200

Bit 7-4

Parity even odd none

This manual is related to the following products:

Modbus Cube I/O MR-DIO4/2 Modbus Cube I/O MR-DO4 Modbus Cube I/O MR-DI10 Modbus Cube I/O MR-DI4 Modbus Cube I/O MR-AI8