VorTek Pro-T, Instruction Manual

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Series M22/M23/M24 Instruction Manual Chapter 4 Serial Communications
M-000-00010 4-11
The following four selections are available in this menu; when selecting an
item, the protocol is changed immediately without having to press the
Enter key.
0-1:2-3 Most significant register first, most significant byte first (default)
2-3:0-1 Least significant register first, most significant byte first
1-0:3-2 Most significant register first, least significant byte first
3-2:1-0 Least significant register first, least significant byte first
Table 4-1.Byte Order
Note that all of the registers are affected by the byte order, including strings and
registers representing 16-bit integers; the register order only affects the order of
those registers representing 32-bit floating point and long integer data, but does
not affect single 16-bit integers or strings.
Modbus Protocol
The Modbus RTU protocol is supported in this implementation. Supported baud
rates are 1200, 2400, 4800, 9600, 19200, 38400, 57600, and 115200. The default
baud rate is 19200 baud. Depending upon the Modbus protocol selected, data are
transmitted in 8-bit data frames with even or odd parity and 1 stop bit, or no
parity and 2 or 1 (non-standard) stop bits.
The current Modbus protocol specification does not define register usage, but
there is an informal register numbering convention derived from the original
(now obsolete) Modicon Modbus protocol specification, and used by many
vendors of Modbus capable products.
Registers Usage Valid Function Codes
00001 – 09999 Read/write bits ("coils") 01 (read coils) 05 (write single coil)
15 (write multiple coils)
10001 – 19999 Read-only bits ("discrete inputs") 02 (read discrete inputs)
30001 – 39999 Read-only 16 bit registers ("input
registers"), IEEE 754 floating point
register pairs, arbitrary length strings
encoded as two ASCII characters per 16-
bit register
03 (read holding registers) 04 (read
input registers)
40001 – 49999 Read/write 16-bit registers ("holding
registers"), IEEE 754 floating point
register pairs, arbitrary length strings
encoded as two ASCII characters per 16-
bit register
03 (read holding registers) 06 (write
single register) 16 (write multiple
registers)