Craftsman G10-0R7G-2SB Manual page 138

Data format: start bit, 8 data bits, parity bit and stop bit. The data format is described
in the following table: In RTU mode, the new frame always starts with a silence of at least
3.5 bytes of transmission time. On a network that calculates the transmission rate at baud
rate, 3.5 bytes of transmission time can be easily grasped. The data fields that are
transmitted next are: slave address, operation command code, data, and CRC check
word. Each domain transmission byte is hexadecimal 0...9, A...F. Network devices always
monitor the activity of the communication bus. When the first domain (address
information) is received, each network device acknowledges the byte. As the transmission
of the last byte is completed, there is a similar 3.5-byte transmission time interval for
identifying the end of the frame, after which a new frame transmission will begin.
The information of a frame must be transmitted in a continuous stream. If there is
more than 3.5 bytes before the end of the entire frame transmission, the receiving device
will clear the incomplete information and mistakenly believe that the next byte is new. The
address field part of a frame. Similarly, if the interval between the start of a new frame and
the previous frame is less than 3.5 bytes, the receiving device will consider it to be the
continuation of the previous frame. Due to the disorder of the frame, the final CRC is
corrected. The verification value is incorrect, resulting in communication failure. Standard
structure of RTU framesÿ
Frame header START
Slave address
ADDR
Functional domain CMD
Data field
DATAÿ N-1ÿ &DATA
ÿ 0ÿ
T1-T2-T3-T4ÿ 3.5 bytes of transmission timeÿ
field
Communication addressÿ 0~247ÿ Decimalÿ
ÿ 0:broadcast addressÿ
03Hÿ Read slave parametersÿ
06Hÿ Write slave parameters
2*N bytes of data, this part is the main content of
communication, and also the core of data exchange in
communication.
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