Emerson Commander SX, Руководство для продвинутых пользователей

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134
ADVANCED USER GUIDE
Commander SX
IP66/Nema 4X variable speed drive
OPERATION WITH MODBUS RTU
CONTROL TECHNIQUES
3854 en - 03.2008 / b
10.40
: Status word 21.4 - MODBUS RTU
21.4.1 - General
The MODBUS RTU protocol is a master-slave type protocol
(a single master per network).
Note: If the CT Comms cable is used, the baud rate is limited
to 38400 baud.
21.4.2 - Description of exchanges
Exchanges are initiated by the master, which sends its
request: if the slave concerned has understood it, it sends its
response. Each frame (question or response) contains four
types of data:
- The address of the slave concerned which receives the
question frame (master request) or the address of the slave
which sends the response frame (encoded on one byte)
- The function code which selects a command (read or write
words, bits etc) for question and response frames (encoded
on one byte)
- The data field containing the parameters relating to the
command (encoded on "n" bytes)
- The frame CRC, calculated on sixteen bits, which is used to
detect transmission errors.
The frame is terminated with a minimum silence period,
equivalent to the transmission time for 3.5 characters (e.g. at
19200 baud, the silence period must be at least 1/19200 x 11
bits x 3.5, i.e. 2 ms). This silence period indicates the end of
the message, and the slave can start to process the
transmitted data.
All data is encoded in hexadecimal format.
Bits of
status
word
10.40
Corresponding
parameters
Drive status
0
10.01
Drive healthy
1
10.02
Drive active
2
10.03
Zero speed
3
10.04
Running at minimum speed
4
10.05
Below set speed
5
10.06
At speed
6
10.07
Above set speed
7
10.08
Nominal load reached
8
10.09
Drive output at current limit
9
10.10
Drive regenerating
10
10.11
Braking IGBT active
11
10.12
Braking resistor alarm
12
10.13
Direction commanded
13
10.14
Direction running
Description Characteristics
Normal physical layer for
multi-drop operation 2-wire RS485
Bit stream Standard UART asynchronous
symbols with Non-Return to
Zero (NRZ)
Symbol Each symbol consists of:
1 start bit
8 data bits (least significant bit
transmitted first)
1 or 2 stop bits depending on
11.27
Baud rate 300, 600, 1200, 2400, 4800,
9600, 19200, 38400, 57600,
115200 baud
Slave Function
Message data
16-bit Silence
address code CRC interval
All master requests will lead to a response from a single slave. The slave will respond within the maximum allotted time (the
minimum response time is never less than the silence period).
Master request Master request
Frame detect
Slave frame
processing
Minimum silence period
Slave
response time
Slave response
Minimum silence period