UART pin out for ModBus master

[Alan Tilley]

I am using the OCG-E serial port as an embedded ModBus interface for a Master on a multi-drop network. I have the 80 pin definition in the developer Guide and want to verify the I/O descriptions before i commit to the PCB.

The way i read the description it talks as a DCE i.e. TXD_1 is an input from the DTE transmitted data. Therefore, form the point of view of a OCG-E ModBus master the RXD_1 is the transmit output from the OCG to ModBus transmitter and TXD_1 the input from the ModBus transmitter.

Also related is the CTS_1 output when the UART is ready to receive another byte from the ModBus transmitter.

I used the In/Out colume to decode this. Is there a schematic available for the OCG-E circuit board?

Also can the EVDDA 3.3 voltage source on pin 41 be used for supplying any external loads? If so how much?

[Tim Gunn]

Hi Alan

You are correct on the pin out.

TXD_1 is the serial input
RXD_1 is the serial output
CTS_1 is the flow control output to indicate when the TXD_1 is ready or not ready to accept data. (Low active indicates ready)

The EVDDA pin is only for the Ethernet transformer and works with pins ERX+- and ETX+-. Cannot be used for anything other than Ethernet transformer connections.

No schematic is available for the OCG-E

Regards

-Tim

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