53A-420 PRESORTING ARINC 429 RECEIVER CARD
• Presorting allows the system controller to operate in real time
• Operates in Single-label or All-label modes
• Built-in error detection capability
• Capable of real-time simulations
The Presorting Receiver Card is used to receive data from the Mark 33 DITS (Digital Information Transfer System) found on civil aircraft and reform at the data received into 8-bit bytes for retransmission to the system controller.
A unique presorting feature is provided on the Receiver Card to solve the data rate problem imposed on the system controller by the DITS bus. This problem can be stated as follows: the DITS bus can have a data rate of up to 100,000 bits per second, but some labels may appear only once every 1/2 second. Without presorting, finding the most current message of a particular label might require that the system controller sift through a continuous stream of 50,000 data bits.
With presorting, the DITS data is sorted and stored in RAM that is located on the Receiver Card. This allows immediate access by the system controller to the most current DITS data associated with a particular label. The presorting can operate in one of two modes:
In this mode, the Receiver Card has 256 RAM storage registers which represent all possible labels of the 32-bit DITS word. The Receiver Card will constantly monitor the incoming data and refresh the appropriate register, insuring the most current DlTS word for all labels is always available to the system controller.
In this mode the system controller sets a “trigger label.” The Receiver Card then monitors the incoming data for the unique trigger label, and when found, stores the associated DITS word in RAM. This feature allows the Receiver Card to sequentially store up to 256 words from a single label.
In either mode, the system controller can read “on-the-fly” (read without interrupting the loading of new data) a specified DITS word from RAM. This feature is provided to prevent the RAM from missing a new update while being read by the system controller.
LEDs provide Built-In-Test Equipment (“BITE”) for the Receiver Card. The data detect LED will be lit whenever data is being transmitted over the DlTS bus to the Receiver Card. The receiver data error LED will be lit whenever the Receiver Card detects an invalid DITS word. The mode LED will be lit when the Receiver Card is in the All-label mode.
Boeing Electronics Support Division Hybrid Receiver.
Direct to ARINC 429 data bus.
Bus terminations provided.
Received Data Error Detection:
Parity, word length and inter-message word gap.
24 x 256 read “on-the-fly.”
Bit Rate (programmable):
Fast, 100 Kilobits per second.
Slow, 12.0 to 14.5 Kilobits per second.
Fast or Slow Rates can be varied ±10%.
OPT 01, defeat parity checking.