Communication Error Management - LAUMAS TLU Installation And User Manual

DELAY parameter in the settings menu for the serial connections, allows the instrument to respond
with a further delay and this directly influences the number of interrogations possible in the unit of
time.
For additional information on this protocol refer to the general technical specifications
PI_MBUS_300.
In general queries and answers toward and from one slave instrument are composed as follows:
FUNCTION 3: Read holding registers (READ PROGRAMMABLE REGISTERS)
QUERY
Address Function
A 0x03
Tot. byte = 8
RESPONSE
Address Function
A 0x03
Tot. byte = 3+2* No. registers + 2
where: No. registers = Number of Modbus registers to write beginning from the address no. 1;
No. byte = Number of bytes of the following data;
FUNCTION 16: Preset multiple registers (WRITE MULTIPLE DI REGISTERS)
QUERY
Address Function Ind. 1st reg. No. reg. No. bytes Val.reg.1 Val.reg.2 2 byte
A 0x10
Tot. byte = 7+2* No. registers +2
RESPONSE
Address Function Ind. 1st reg. No. reg. 2 byte
A 0x10
Tot. byte = 8
where: No. registers = Number of Modbus registers to read beginning from the address no. 1;
No. byte = Number of bytes of the following data;
Val.reg.1 = Contents of the register beginning from the first.
The response contains the number of registers modified beginning from the address no. 1.
The communication strings are controlled by way of the CRC (Cyclical Redundancy Check).
In case of communication error the slave will not respond with any string. The master must consider
Add. 1st register No. registers 2 byte
0x0000
No. bytes 1st register 2nd register 2 byte
0x04 0x0064
0x0000 0x0002
0x0000 0x0002

COMMUNICATION ERROR MANAGEMENT

0x0002 CRC
0x00C8 CRC
0x04 0x0000
CRC
- 29 -
0x0000 CRC