Delta PLC与Linux电脑Modbus RTU通信断电后无响应问题求助

我有一台Delta PLC和一台Linux电脑，一直采用Modbus RTU方式连接通信，之前用下面这段代码运行完全正常：

from pymodbus.client import ModbusSerialClient
import struct
client = ModbusSerialClient(port='/dev/ttyUSB0', baudrate=9600, timeout=1)

if client.connect():
    print("Connected to modbus device!")
    
    register = int(input("Enter your register: "))
    response = client.read_holding_registers(address=register, count=8)
    high_word = response.registers[0]
    response_2 = client.read_holding_registers(address=register + 1, count=8)
    low_word = response_2.registers[0]
    
    combined_value = (low_word << 16) | high_word
    combined_value_2 = (high_word << 16) | low_word
    signed_value = struct.unpack('i', struct.pack('I', combined_value))[0]
    print(high_word, low_word)    
    print(combined_value)
    print(signed_value)

但经历一次长时间断电后，不管我怎么操作，代码都会报错。现在的报错信息如下：

Connected to modbus device!
Enter your register: 6096
No response received after 3 retries, continue with next request
Traceback (most recent call last):
  File "/home/admin/plc_monitoring/read.py", line 9, in <module>
    response = client.read_holding_registers(address=register, count=8)
  File "/home/admin/plc_monitoring/venv/lib/python3.9/site-packages/pymodbus/client/mixin.py", line 114, in read_holding_registers
    return self.execute(no_response_expected, pdu_reg.ReadHoldingRegistersRequest(address=address, count=count, dev_id=slave))
  File "/home/admin/plc_monitoring/venv/lib/python3.9/site-packages/pymodbus/client/base.py", line 186, in execute
    return self.transaction.sync_execute(no_response_expected, request)
  File "/home/admin/plc_monitoring/venv/lib/python3.9/site-packages/pymodbus/transaction/transaction.py", line 120, in sync_execute
    raise ModbusIOException(txt)
pymodbus.exceptions.ModbusIOException: Modbus Error: [Input/Output] No response received after 3 retries, continue with next request

我已经尝试了以下操作，但都没有解决问题：

• 用WPL Soft重新向PLC写入程序
• 换用主电脑运行程序
• 更换了通信线缆

更奇怪的是，Modbus Poll工具还能正常和PLC通信，但我的Python代码就是无法获取响应，实在找不到问题所在，有没有大佬能帮忙排查一下？

备注：内容来源于stack exchange，提问作者Karanveer Singh