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1300 Henley Court Pullman, WA 99163 509.334.6306 www.digilentinc.com PmodRS485 Reference Manual Revised April 12, 2016 This manual applies to the PmodRS485 rev. B Overview The Digilent PmodRS485 provides signal and power isolation for high speed communication lines utilizing the RS- 485 communication protocol. Features include: High-speed RS-485 communication module Isolated RS-485/RS-422 interfaces for use in noisy environments 16Mbps maximum data rate Connect up to 256 nodes on one bus Differential half or full-duplex communication Thermal shutdown and 15kV ESD protection 6-pin Pmod port with UART interface Library and example code available in resource center The PmodRS485. 1 Functional Description The PmodRS485 utilizes Analog Devices ADM2582E to facilitate RS-485 and RS-422 serial communication protocols between devices in environments with high electrical noise. The ADM2852E provides both signal and power isolation allowing for accurate data transfer across long distances. Data transmission rates of 16 Mbit/s can be achieved. 2 Interfacing with the Pmod The PmodRS485 communicates with the host board via the UART protocol. In order to transmit data, the Driver Enable line must be pulled to a logic level high voltage state similarly, in order to receive data, the Receive Enable line must be driven to a logic level low voltage state. Truth tables indicating the status of the various pins of the PmodRS485 are provided below: Copyright Digilent, Inc. All rights reserved. DOC : 502-310 Page 1 of 4 Other product and company names mentioned may be trademarks of their respective owners. PmodRS485 Reference Manual Inputs Output A-B Voltage ~RE RxD Difference -0.03V Low or Not Connected High -0.2V Low or Not Connected Low -0.2V < A-B < -0.03V Low or Not Connected Don t Care Inputs Open Low or Not Connected High Don t Care High High Impedance Table 1. Receiving. Inputs Output DE TxD Y Z High High High Low High Low Low High Low Don t Care High Impedance High Impedance Table 2. Transmitting. Pin Signal Description 1 ~RE Receive Enable 2 TxD Transmit Data Signal Description 3 RxD Receive Data A Input A 4 DE Driver Enable B Input B 5 GND Power Supply Ground Z Output Z 6 VCC Positive Power Supply (3.3V/5V) Y Output Z Table 3. Pinout description table: Pmod Header J2. Table 4. Screw terminals. RE B-input TXD JP1 A-input RXD RS485 Transceiver DE Y-output GND Z-output VCC Figure 1. PmodRS485 functional block diagram. Copyright Digilent, Inc. All rights reserved. Page 2 of 4 Other product and company names mentioned may be trademarks of their respective owners.