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This block is part of the MAX Technologies ARINC 429 library. It is associated to a single OpMaxT A429 Ctrl block.

The OpMaxT A429 Send block has two purposes:

  • allows the user to define the configuration of a transmit operation,
  • provides the ARINC 429 words to be transmitted.

The block controls only one Arinc 429 transmitter on the IP module.


Controller IDThis parameter, represented by an integer value, is used to associate the OpMaxT A429 Send block to only one controller block responsible for the hardware configuration.
Channel NumberSpecifies the number of the Arinc 429 transmitter controlled by this block. Valid values for this parameter are in the range 0 to 7 for the IPM429-E-8T-8R module.
Send Type

The user may choose one of the following transmission configurations:

  • Asynchronous: used to transmit unscheduled arinc 429 words. When selected, the SendData input becomes available. Use this input to implement an algorithm that configures a transmit operation each time step or once every few time steps. No time tag is associated to the words to be transmitted.
  • Scheduled send: use this option to configure a scheduled major/minor frame transmission using the Repeat Rate and Time Offset parameters that become available when this option is chosen.
Repeat Rate

This parameter, together with Time Offset, allow the user to schedule a major/minor frame transmission. The major frame is represented by the total rows and each row represents a minor frame equal to the Time Step duration.

The Repeat Rate parameter defines:

  • The number of the minor frames to be included in a major frame.
  • The repeat rate for every input arinc 429 word inside every minor frame.

In general, the user input for this parameter must be represented by an m-by-n matrix, where m represents the number of minor frames and n is equal to the number of arinc 429 words to be transmitted (contact Opal-RT if you need to use more than the current maximum of 65536 elements). The matrix elements for the Repeat Rate must be '0' or '1':

  • '1' means that inside that minor frames, the corresponding arinc 429 word is being transmitted, while
  • '0' means that it will be omitted.

Note: Knowing that it takes 2.56 ms to transmit an arinc word (32 bit) at 12,5 kHz and 0.32 ms at 100kHz, it is the user responsibility to make sure that the model calculation step is large enough to allow the transmission of all the input data words at the configured speed.

Time OffsetSimilar with the Repeat Rate, this parameter input must be a m-by-n matrix, ' m' representing the number of minor frames scheduled inside a major frame (total number or rows) and 'n' representing the number of arinc 429 words received as input to the OpMaxT_A429_Send block. The matrix elements are doubles and represent a percentage of the minor frame duration where data has to be sent on the ARINC 429 bus.
Input Data Format

Two options are available:

  • Raw Data- assumes the input is an already formatted arinc 429 word. The driver sends it "as is" if the parity check is disabled. Otherwise, the firmware may modify the parity bit.

Note: when formatting data, please be informed that the IP module firmware swaps the label section of the ARINC 429 word (bit 0 to 7) so the LSB will be transmitted first.

  • Fields Detailed - the user may input each field of the arinc 429 word depending on its size (25 bit or 32 bit). In preparation of the transmission, the driver will convert them to arinc 429 words.
SpeedSelect the transmission speed between low 12.5kHz or high 100kHz.
Interword GapSelect the gap between two successive arinc 429 words. When not checked, the default value of 4 bit times is used. When checked, a new parameter becomes visible and lets you choose a value between 0 and 15.75 microseconds.
ParityThis parameter allows the control of the parity. When checked, a new parameter becomes available, and the user may choose between odd or even parity check.
Channel MuteThis parameter allows the user to stop or to restart the transmit operation. When checked, a new input becomes available and the user is able to dynamically control the block's operation.
Select the Word SizeThis parameter allows the user to choose the size of the arinc 429 words to be transmitted. It has no impact on the transfer duration because the driver will pad the 25 bit word with '0's so, it will send 32 bit words.
Label MuteThis parameter allows the user to stop or restart the transmission of a specific label. When checked, a new input becomes available and the user is able to dynamically control the transmission of labels. This option can be selected only when the Input Data Format is Fields Detailed.


Send DataThis input is available only for Asynchronous send. The block performs the transmission only when this inputis equal to 1.
SSM (Sign/Status Matrix)This 2-bit input is available only for Fields Detailed transmit operation, and only if Selected Word Size is 32 bit. It represents the Sign/Status Matrix.

This input represents the data to be transmited on the selected transmitter channel.

  • For Fields Detailed transmit operation this input represents the 19-bit data field of the arinc 429 word.
  • For Raw Data transmit operation, this input represents the complete 25 or 32 bit arinc 429 word (except for the parity bit).
SDI (Source/Destination Identifier)This 2-bit input is available only for Fields Detailed transmit operation, and only for 32-bit word size. It represents the Source/Destination Identifier.
LabelThis 8-bit input is available only for Fields Detailed transmit operation. It represents the first 8 bits of each arinc 429 word.
Channel Mute

This input becomes available only if Channel Mute parameter is checked. Valid values for this input are 0 and 1:

  • 1 means that the transmit operation is enabled;
  • 0 means that the transmit operation is disabled.
Label MuteThis input becomes available only if Label Mute parameter is checked. This input receives a vector of arbitrary size (maximum size is 256). Although the vector can consist of any integer, only the elements between 0 to 255 will be counted as a valid label.


Error: The following error codes may be returned:

Error CodeMessage
0All the input ARINC 429 words have been sent .
1The transmit operation has been blocked using the channel mute input.

Characteristics and Limitations

Direct FeedthroughYes
Discrete sample timeYes
XHP supportNo
Work offlineNo

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