The M550, M560 and M570 have the facility to re-order their Modbus 3X registers to suit an existing Modbus network.
The integrated register re-ordering function (‘Registers’ button) in the MultiView Program provides an easy method of achieving this.
If MultiView isn’t going to be used, Modbus function code 1Fh (31) can be used to request this data and Modbus function code 1Eh (30) can be used to send a string of data to set the order of the registers. The order will automatically be saved in EEPROM.
UNLIKE THE 3X AND 4X REGISTERS, THESE DATA ARE WORD WIDE INTEGER.
It is important to remember that each register in the packet’s data field contains two references to the registers to be re-ordered.
A sample read packet will look like this:-
[Node][1F][start address(always 0000h)][No. of Double Registers Required][CRC(2 bytes)]
e.g. To read the 41 Modbus registers in node 23h a request to send 21 (15h) registers is made:-
[23h][1Fh][0000h][0015h][CRC(2 bytes)]
A sample write packet will look like this:-
[Node][1E][start address(always 0000h)][No. of Double Registers][Data length in bytes] [REGISTERS][CRC(2 bytes)]
e.g. To set the 41 Modbus registers to their default order in node 23h:-
[23h][1Eh][0000h][0015h][29h][0102h][0304h][0506h][0708h][090Ah][0B0Ch][0D0Eh]
[0F10h][1112h][1314h][1516h][1718h][191Ah][1B1Ch][1D1Eh][1F20h][2122h]
[2324h][2526h][2728h][29xx][CRC(2 bytes)]
N.B. xx = don’t care.
Sample Coding
WRITE
1) Set the default order
Slave Address = 1
Writing – code 30 (1E hex)
Message Packet To SLAVE
01 1E 00 00 00 15 29 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F 20 21 22 23 24 25 26 27 28 29 E1 A3
Response Packet From SLAVE
01 1E 00 00 00 15 68 07
2) Move registers W Sum (position 10), VAr Sum (position 12) and VA Sum (position 11) into the first three positions in the table so that the measurements can be retrieved from the slave by reading just the first three registers (30001-30003 or 42001-42003).
Slave Address = 1
Writing – code 30 (1E hex)
Message Packet To SLAVE
01 1E 00 00 00 15 29 0A 0C 0B 01 02 03 04 05 06 07 08 09 0D 0E 0F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F 20 21 22 23 24 25 26 27 28 29 FB E5
Response Packet From SLAVE
01 1E 00 00 00 15 68 07
READ
N.B. Asking for more registers than the M550/M560/M570 supports will not result in an error.
1) Default order
Slave Address = 1
Reading – code 31 (1F hex)
Asking for 24 (18 hex) word registers (48 bytes)
Message Packet To SLAVE
01 1F 00 00 00 18 94 02
Response Packet From SLAVE
01 1F 00 00 00 18 30 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F 30 85 BA
2) W Sum, VAr Sum, VA Sum order
Slave Address = 1
Reading – code 31 (1F hex)
Asking for 24 (18 hex) word registers (48 bytes)
Message Packet To SLAVE
01 1F 00 00 00 18 94 02
Response Packet From SLAVE
01 1F 00 00 00 18 30 0A 0C 0B 01 02 03 04 05 06 07 08 09 0D 0E 0F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F 30 30 DD