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Legacy Serial Port

Send and receive data over mainboard baseboard serial port

  • Legacy Serial Port block

Simulink Real-Time / RS232 / Mainboard


The Send/Receive block sets up the serial interface to send and receive basic character streams. This block has basic First In, First Out (FIFO) Read blocks inside the subsystem. It generates output as an array of packed integers (settable at 8 bits, 16 bits, or 32 bits). Characters appear in the lower byte and received status information appears in the upper byte.



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Vector of the data used to transmit over the port.

Data Types: int8 | int16 | int32 | uint8 | uint16 | uint32


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Vector containing data that has been received from serial port.

Data Types: int8 | int16 | int32 | uint8 | uint16 | uint32


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This parameter specifies the port for which you want to view or modify parameters. If using USB-to-serial adapters, the target computer detects these adapters as serusb1, serusb2, and so on in the order that the adapters are connected to the serial devices. The order of port assignment is retained through the power cycle of the target computer or serial device if there is no change in the connections to the ports.

Programmatic Use

Block Parameter: port

Select a baud for transmitting and receiving data through the modem.

Programmatic Use

Block Parameter: baud

Select the number of bits that encode a character.

Programmatic Use

Block Parameter: width

Select the number of stop bits for the character stream.

Programmatic Use

Block Parameter: nstop

Select a parity for checking data integrity.

Programmatic Use

Block Parameter: parity

To enable the Request To Send/Clear To Send (RTS/CTS) handshake of the Universal Asynchronous Receiver-Transmitter (UART) for flow control, select this check box. Serial controllers use the RTS/CTS handshake to prevent data loss due to hardware FIFO overflow on the device that you are sending to.

Usually, the interrupt service routine executes quickly enough to empty the FIFO. If your model gets FIFO overruns, select this check box.

Programmatic Use

Block Parameter: ctsmode

Enter the maximum number of elements that you want returned by a single call to this block. The block uses this parameter to set the output vector width.

If you select the Read to delimiter check box and if the block does not find the delimiter before it reads Receive maximum read characters, the output vector is empty.

Programmatic Use

Block Parameter: maxread

Enter the minimum number of characters to read. If the FIFO does not contain at least this number of characters, the output vector is empty.

Programmatic Use

Block Parameter: minread

For the block to return all characters in the FIFO, up to and including the specified delimiter, select this check box.

If the buffer has errors, such as framing errors, the modem returns characters regardless of the presence of the delimiter. These returned characters help diagnose errors such as mismatched baud rates.

If the block does not find the delimiter before it reads Receive maximum read characters, the output vector is empty.

Programmatic Use

Block Parameter: usedelimiter

Enter the numeric value of the character that is the message delimiter. Any value from 0 to 255 is valid. The common case looks for 10 (line feed) or 13 (carriage return).

Programmatic Use

Block Parameter: delimiter

This parameter specifies the data type of the receiver. The 8-bit data types produce a NULL-terminated character vector in the output vector.

For 16-bit and 32-bit data types, the first element contains the number of valid elements in the rest of the output vector.

For 8-bit data types, only the character data is in the output vector, and a NULL terminator is appended. The 16-bit or 32-bit wide data types cause the error status from the UART to be placed in the second byte of each data element. (The error status contains the parity, overrun, framing, and break bits.) The character data is in the bottom 8 bits of each element. The first element of the vector contains the number of data elements that follow.

Programmatic Use

Block Parameter: odtype

This parameter specifies the receive FIFO size in bytes.

Example: 1024

Programmatic Use

Block Parameter: fifosize

Data Types: int32

This parameter specifies the data type of the transmitter. The 8-bit data types require a NULL-terminated character vector in the input vector.

The 16-bit and 32-bit data types reserve the first full element to contain the number of elements to expect in the rest of the input vector. Only the low-order byte of each data element is sent. Setting this data type enables a wider data type to hold the bytes.

If the data stream requires a NULL byte, select one of the 16-bit or 32-bit data types. Because the 8-bit data types are NULL-terminated character vectors, the NULL byte terminates the character vector.

Programmatic Use

Block Parameter: idtype

Enter the base sample time or a multiple of the base sample time. -1 means that sample time is inherited.

Programmatic Use

Block Parameter: sampletime

Version History

Introduced in R2008a

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