CIRCUTOR QNA500 series - Manual (Page 84)

POWER QUALITY ANALYZER QNA500 8IO
QNA500 8IO Instruction manual 84 / 111
11.- COMMUNICATIONS PROTOCOLS
QNA500 has various communications protocols, as a result of its powerful internal management
system. It can send data to SCADA systems, market PLC systems or any industrial system that uses
the following protocols. These protocols are available on the 3 communications ports of the M-BASE
module.
11.1.- MODBUS / RTU
QNA500 8IO uses the Modbus/RTU ® protocol as the main communications protocol. This is a query-
response based protocol. The query frame format is as follows:
NPAAXXXXYYYYCRC.
NP: Peripheral number configured in the system.
AA: Modbus function to be performed.
XXXX: Memory position of the unit where the function will be started. (For ex., when AA=04 is
the read function).
YYYY: Read positions that are read or written from the XXXX position (depending on the AA
function).
CRC: 16-bit error detection code. (generated automatically).
The response format will be as follows:
NPAABBCCCC.. CRC
NP: Peripheral number responding to the query.
AA: Function responding to the query.
BB: Number of bytes of the response.
CCCC: Value that contains the record
...
CRC: Error detection registry.
Refer to the standard Modbus ® protocol for more information.
The Modbus memory map is attached to the communications appendix.
The following port must be used when establishing communications through the Ethernet port: 20003