RS-232/422/485 Write Hardware FIFO (Composite)

RS-232/422/485 Write Hardware FIFO block


Simulink® Real-Time™ Library for RS-232


The Write Hardware FIFO block writes the data from the input port (labeled E) to the FIFO in the I/O module UART for this port.

The following pseudocode describes the behavior of this FIFO.

if (enable is false)
     if (input data empty)
          disable transmitter buffer empty interrupt
          copy input data to HW FIFO

In words: if the enable port (input port E) becomes true and the input data has length 0, then the block turns off the transmitter buffer empty interrupt. Otherwise, the block adds input data to the FIFO.

The Commtech/Fastcom and Quatech® boards and blocks will be removed in a future release. Do not use them in new models. Instead, use boards and blocks available from

Block Parameters

Base address (Mainboard, ISA boards)

Enter the base address of the UART for which you want to write the FIFO.


From the list, choose a port. This is the port to which this block writes data.

Assert on Transmit (RS-422/485 boards)

Select None, RTS, or DTR. The board asserts no bit, the RTS bit, or the DTR bit in the modem control register upon data transmission.

For half duplex operation, set the jumper on the board to send either RTS or DTR signals to the transmit enable gate. See the board documentation for further information.

Slot (PCI boards)

If only one board of this type is in the target computer, enter -1 to automatically locate the board.

If two or more boards of this type are in the target computer, enter the bus number and the PCI slot number of the board associated with this driver block. Use the format [BusNumber, SlotNumber]. To determine the bus number and the PCI slot number, type:

tg = slrt;
getPCIInfo(tg, 'installed')

Introduced before R2006a

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