RS485 chip ground all connected together, AB line is not pulled up and down (R66 R67 attachment schematic not added), communication is OK. Now that the aging machine has increased the quality of the
communication, it is suspected that the pull-up resistors are not connected. Therefore, the addition of a 4.7K pull-up and pull-down resistor indicates that the communication has improved.
If I want to add 100 machines, if the pull-down resistor 47K, because it is a common ground, is not the pull-down equivalent resistance is 470 ohms? If the machine increases again, will there be a load pull death?