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1.9 SERIAL
MODbUS INTERFACE
The 9099's asynchronous serial Modbus interface provides RS-232 single-ended
signals and RS-485 (RS-422) differential signals with an internal termination
network. Signals are selected by internal jumpers.
1.9.1 Modbus RTU Message Format
Messages conform to the Modbus RTU format and include the device address,
command, register number, data and CRC formatted as binary bytes. Supported
Modbus commands when using VXI-11.3 or raw socket protocol are: 01, 02,
03, 04, 05, 06, 07, 08, and 16 for integer values and commands 03 and 16 for
floating point 32-bit values.
Integer range
16 bits or 65,536
Floating point
IEEE-754
There are no Modbus command restrictions when using the Modbus TCP/IP pro-
tocol. Message size and responses cannot exceed the 255 byte packet size.
1.9.2 baud Rates
Although Modbus RTU devices typically support only 9600 and 19200 baud,
the 9099 is setable to the following baud rates. The 9099 selects the next higher
standard rate when a nonstandard rate is entered.
1200, 2400, 4800, 9600, 19200, 38400, 57600, and 115200 baud.
1.9.3 Data Character Formats:
Data bits 7 or 8 data bits per character
Parity
none, even or odd
Stop bits 1 or 2 stop bits per character
1.9.4 RS-232 Specifications
All units have single-ended RS-232C drivers and receivers that are designed to
operate with up to 50 feet of cable. Hardware handshaking is not supported.
Signals have 15 Kv ESD protection.
Transmit +5 Vdc = Logic "0" or On
Levels -5 Vdc = Logic "1" or Off
Содержание 9099
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