ARINC 429/575 Six Channel, Tx/Rx (Module A4)68C3 Operations Manual North Atlantic Industries, Inc. 12/19/2014Rev: 2014-12-19-0947 www.naii.com Page 56 of 330Tx (Transmit) Buffer (FIFO)Type: unsigned character wordRange: 0 to FFFFhRead/Write: WInitialized Value: Not ApplicableThis register is the transmit data FIFO. In immediate or triggered FIFO modes, transmit data is placed here priorto transmission. ARINC data words are 32-bits and are placed into the FIFO 16bits at a time starting with theUPPER 16 bits. The FIFO level is incremented after the LOWER 16 bits are written. This memory is shared withthe Tx Message memory and is only available in Tx FIFO modes.REGISTER D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 FUNCTIONTRANSMIT FIFO D D D D D D D D D D D D D D D D D=DATA BITRx (Receive) Buffer (FIFO)Type: unsigned integer wordRange: 0 to FFFFhRead/Write: RInitialized Value: Not ApplicableIn FIFO receive mode, the received ARINC messages are read back from here. Perform three reads from thisregister to retrieve the Status word, the upper 16 bits of the ARINC data word, and the lower 16 bits of the ARINCdata word, respectively. If Time Stamping is enabled, perform 2 more reads to retrieve the upper and lower 16bits of the timestamp respectively.In Mbox receive mode, this FIFO contains the 10 bit SDI/Label of newly received messages. This provides a list tothe user showing which mailboxes contain new messages since the last time this FIFO was read.REGISTER D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 FUNCTIONFIFO mode X X X X X X X X X X X X X X N PE Message Status WdFIFO mode D D D D D D D D D D D D D D D D Data WordsMBOX mode: X X X X X X A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 SDI/Label of received ARINC wordPE = Parity Error ‘1’ Calculated parity does not match the received parity bitN = New message ‘1’ Message has not been read yetA10 – A1 Lower 10 bits of the ARINC data word where A8 is the msb of the Label and A1 is the lsb.A10 and A9 are the SDI bits.
