Rs485 Communication Circuit - Veichi AC310 Service Manual

3.5 RS485 Communication Circuit

1. Circuit description
RS485 communication is a typical half-duplex communication. With SP485EEN-L as the
core and its peripheral circuits, up to 32 machines can communicate. 。
RS-485 uses balanced transmission and differential reception, and therefore has a strong
ability to suppress common mode interference. The bus transceiver has a high sensitivity and
can detect voltages as low as 200mV, so that the transmitted signal can be recovered from
kilometers away.
As half-duplex communication, only one point can be in the transmit state at any time,
therefore, the transmit circuit must be controlled by an enable signal.
2. Input and output interface definitions and their metrics
Interface
definition
A+
B-
Input
The amplitude of A+ relative to B- is +5V, with a threshold of not less than
side
200mV, which usually requires enough margin to include termination.
Resistances will reduce the signal amplitude, but can reduce the signal
reflection, but is beneficial to the reliability of communication.
Output
RXD1
side
RS485 Communication Circuit
A+ input/output interface for RS485 communication.
B- input/output interface for RS485 communication.
A+/B- Differential input signals processed by the SP485EEN-
L and fed to the CPU
AC310 Universal AC Drive Service Manual
Maximum through-
current 230mA, DC
impedance 1.0Ω
Related notes
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