NanoBoard 3000 - RS-232 Serial Interface

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The NanoBoard 3000 provides a PC-style RS-232 serial interface. A DB-9 Male connector is used to provide a serial port, wired as a DCE (Data Communication Equipment), in accordance with the EIA-574 standard. Connection to a host PC (wired as a DTE (Data Terminal Equipment)) can be achieved using a null modem serial cable.

RS-232 serial interface port.

Signal level translation – CMOS to RS-232 and vice-versa – is provided using a HIN232A high-speed RS-232 Transceiver device (from Intersil). This device has 2 receivers and 2 drivers, the use of which is summarized as follows:

  • Receivers – used for the RXD (pin 2 of connector) and CTS (pin 8 of connector) signals, received from the host PC over the RS-232 interface and subsequently wired to pins of the User FPGA.
  • Drivers – used for the TXD (pin 3 of connector) and RTS (pin 7 of connector) signals, sourced from the design running in the User FPGA device for transmission to the PC over the RS-232 interface.

The HIN232A is powered from the motherboard's 5V supply and incorporates a dual charge pump, requiring four 0.1uF external charge pump capacitors. RS-232 output levels are maintained at a high data rate of 230kbps.

The incoming Data Terminal Ready signal (DTR) – which arrives on pin 4 of the connector – is wired, on the motherboard, directly to the outgoing pins for the Data Set Ready (DSR) and Data Carrier Detect (DCD) signals (pins 6 and 1 of the connector respectively). The Ring Indicator signal (RI) arriving on pin 9 of the connector, is not used.

Location on Board

The DB9M (Male) connector (designated J17) is located along the top edge on the solder side of the board. Looking from the rear, it can be found at the far right, next to the RS-485 connector.

RS-232 Port (as seen from the rear of the board).

The HIN232A device (designated U59) and associated external capacitors are located on the solder side of the board, towards the top-right corner.

HIN232A device and related circuitry.

Schematic Reference

The RS-232 interface circuitry can be found on the following sheets of the motherboard schematics:

  • Sheet 59 (RS232_HIN232.SchDoc, entitled RS232 Communication IC)
  • Sheet 60 (CON_RS232DCE_DB9_TH.SchDoc, entitled RS232-DCE DB9).

Design Interface Component

Table 1 summarizes the available design interface component that can be placed from the FPGA NB3000 Port-Plugin.IntLib, to access and use the RS-232 interface.

Table 1. RS-232 port-plugin component.
Component Symbol
Component Name


Place this component to interface to the HIN232A device and subsequent RS-232 serial port.

Further Device Information

For more information on the HIN232A device, refer to the associated datasheet (fn4316.pdf) available at

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