Pin Description
Last updated
Last updated
Modbus UART Transmit and Receive Pins.
These pins handle UART transmit and receive functions for Modbus data and operate at TTL levels of 3.3V and they are 5V tolerant.
To interface with the field bus, these pins must connect to a suitable transceiver based on the field bus used: RS485, RS422, RS232, or others.
Please note that applying directly field bus (RS485, RS422, RS232, etc.) voltage levels to those pins will permanently damage the device.
For an RS485 fieldbus, use an RS485 transceiver, such as the THVD1330DR, to convert RS485 differential signaling to TTL/CMOS voltage levels. For an RS232 fieldbus, a transceiver like the MAX3221 can be used. Refer to the “Implementation ” chapter for more details.
Modbus Direction Pin.
This pin is typically used in transceivers to control the data flow (sending or receiving). For RS485 transceivers, it connects to the DE and pins of the transceiver.
Modbus Over Serial Line is usually implemented on “Two-Wire” RS485 electrical interface, which operates in a half-duplex topology. Therefore, a direction pin is needed to indicate whether the transceiver should send or receive data. By default, the DIR pin is in a low state, which sets the transceiver to receive mode.
I2C-Compatible Bus Interface Pins.
SCL (Serial Clock Line): This pin is used to synchronize data transfer between the IS4310 device and the Microcontroller or other CPU.
SDA (Serial Data Line): This bidirectional pin is used for both sending and receiving data between the IS4310 and the Microcontroller or other CPU.
Both pins are open-drain and must be pulled up to 3.3V or 5V. The pull-up resistor value should be chosen based on the bus speed and capacitance. Typical values are 4.7kΩ for Standard Mode (100kbps) and 2.2kΩ for Fast Mode (400kbps) at both 3.3V and 5V.
I2C-Serial Interface Speed Selection Pin.
This pin configures the IS4310 internal I2C-Serial Interface timings and filters to properly work with the selected bus speed.
For a 100kHz setting, set the I2CSPD pin to VSS.
For a 400kHz setting, set the I2CSPD to 1.65V (VDD/2) using a balanced voltage divider. This can be achieved by placing two 4.7kΩ resistors from the I2CSPD pin: one to VDD and the other to VSS.
For a 1000MHz setting, set the I2CSPD pin to VDD.
Important Remark
A mismatch between the configured I2C speed and the actual operating I2C speed (e.g., configuring the bus for 100kHz but operating at 1MHz) can lead to an inconsistent state where some I2C messages are processed while others are not.
Ensure a proper match between the actual operating speed and the configured speed at the I2CSPD pin: If your bus works at 100kHz, ensure the I2CSPD pin is tied to VSS. If it works at 400kHz ensure the pin is at 1.65V. If it works at 1000MHz, ensure the pin is at 3.3V.
