TOTALFLOW MODBUS PROTOCOL - Electrical Solutions Corp

1 REV ACTION DRAWN CHECKED APPROVED DATE AA L12040 NORFLEET SHORT HOLLAND 01/12/21 AB NORFLEET 03/02/14 AC D14351 NORFLEET JOHNSON BUSHNELL 03/03/03 AD NORFLEET APPLICATION INFORMATION FOR TOTALFLOW MODBUS PROTOCOL AND PRINTER / CONSOLE FOR BTU-XMTR TABLE OF CONTENT.

2 TOTALFLOW MODBUS PROTOCOL - SEE SH 2 THRU 19 BTU-XMTR PRINTER/CONSOLE COMMANDS - SEE SH 20 THRU 64 PRODUCT LINE LEVEL TOTALFLOW TOTALFLOW PRODUCTS3 DESIGN APPLICATION INFORMATION DATE NORFLEET 01/12/21 DRAWN AI MODBUS AND PRINTER CONSOLE NORFLEET 01/12/21 MODBUS CHECKED SHORT APPROVED SCALE SIZE TYPE DRAWING NO.

3 REV SHEET HOLLAND NONE A AI 2100666 AD 1 OF 64 2100666-AI Rev AD 2 I. Purpose This paper describes the MODBUS communications PROTOCOL for TOTALFLOW Model 8000 BTU Transmitters.

4 II. MODBUS Description The MODBUS PROTOCOL is described in the document entitled Modicon MODBUS PROTOCOL Reference Guide produced by AEG Schneider Automation, Part Number PI-MBUS-300 Rev. G, 1994. MODBUS uses the master, slave communications concept. Slave devices speak only when spoken to by the master. Each slave is identified by an unsigned, one byte number ranging from 1 to 247 (inclusive). A slave must send a single response to a master's request for data. The BTU Transmitter supports the ASCII message frame format and the RTU message frame format.

5 MODBUS ASCII message frame format: Clear BOF Packet LRC EOF Ready 0xff : 2 x Number of bytes in MODBUS packet 8-bits CR LF Clear: This character is an extension used by TOTALFLOW to assist in clearing the communications link of noise and to help certain hardware devices to be able to receive BOF without errors. The Clear Byte can be disabled if required. BOF: A colon (:) character is used to indicate beginning of frame. Packet: The packet field consists of hexadecimal ASCII characters representing the MODBUS packet being sent or received.

6 The number of characters is twice the number of bytes in the MODBUS packet because each packet byte is converted into two hexadecimal ASCII characters ('0'-'9','A'-'F'.) LRC: The error check field consists an 8 bit longitudinal redundancy check calculated over the length of the packet field before it is converted to hexadecimal ASCII. The LRC is calculated by adding together successive 8-bit bytes of the message, discarding any carries, and then two s complementing the result. EOF/Ready: A carriage return and line feed are used to delineate end of frame.

7 The communications parameters for the ASCII format are fixed at 7 data bits, even parity and 1 stop bits. MODBUS RTU Message Frame Format: BOF Packet CRC EOF T1-T2-T3-T4 Number of bytes in MODBUS packet 16-bits T1-T2-T3-T4 BOF: Represents character times of silence with a minimum of 20 milliseconds.

8 Packet: The packet field consists of hexadecimal binary characters representing the MODBUS packet being sent or received. CRC: The error check field consists a 16-bit cyclical redundancy check calculated over the length of the packet field before it is converted to hexadecimal ASCII. The CRC is calculated according to the procedure outlined in the EOF/Ready: Represents character times of silence with a minimum of 20 milliseconds. Note: The design of the BTU Transmitter does not allow strict compliance with the timing requirements of the RTU PROTOCOL .

9 RTU PROTOCOL might not work with some hardware. In this case, use ASCII. The communications parameters for the RTU format are fixed at 8 data bits, no parity and 1-stop bits. Note: Total message frame length cannot exceed 256 bytes. III. Communications Setup The following items can be set from the Printer/Console mode: MODBUS Slave Address: 1-247 BaudRate: 1200, 2400, 4800, 9600, 19200 2100666-AI Rev AD 3IV. TOTALFLOW BTU Transmitter MODBUS Implementation TOTALFLOW MODBUS supports the following subset of the Gould (Modicon) MODBUS defined functions: Code Function Description 03 Read Registers Reads group of registers 06 Set Single Register Sets a single register (Prom Rev AG2015644-005 or above and all 2100528 and 2100986 part numbers) 08 Diagnostics Return Query Data subfunction 00 only.

10 16 Set Multiple Registers Set multiple registers Byte count greater than 128 may cause transmitter failure. Broadcast commands are not supported. Packet formats: Read Registers Address Function Register Quantity (N) 8-bits 8-bits (0x03) 16-bits 16-bits Read Registers Response by BTU Transmitter Address Function Byte Count Data 8-bits 8-bits (0x03)