4
Data Device Corporation
www.ddc-web.com
DD-00429
L-02/10-0
The ARINC CLK input should nominally be 10 times (for High-
Speed Mode) or 80 times (for Low-Speed mode) the desired
ARINC Data Rate. ARINC CLK 0 is used to synchronize chan-
nels Rx0 and Rx1 while ARINC CLK 1 is used to synchronize
channels Rx2 and Rx3.
Filtering and Sorting Rx Data: The receiver circuitry converts
the serial data stream into a 32-bit-wide parallel data word. The
32-bit word is processed internally by a Data Match Processor
(DMP). It compares the incoming data to a table of data initial-
ized by the processor. This determines what incoming data is to
be saved, where it is going to be saved, and if any interrupts are
to be generated. The table of data is stored in a 128 word x 16
bit Data Match Table (DMT) RAM. When a match between the
received ARINC 429 data and the criteria stored in a DMT entry
is found, the received data, the storage address and modes, and
interrupt parameters are passed to the Data Store Processor
(DSP). The storage address in the Receive RAM is the address
of the first matching DMT entry minus 200 hex.
There are three requirements that must be met in order to match
incoming ARINC 429 data to each DMT entry:
1) System Address Label: Bits 0-7 of the DMT are compared
to the System Address Label (SAL) of the incoming ARINC
429 data word. If the DMT SAL entry is zero then the SAL of
the incoming data word is ignored (or considered a match).
2) Source/Destination Bits: Bits 8 and 9 of each DMT entry
are compared to the Source/Destination (S/D) bits of the
incoming ARINC 429 data word. If these bits match, or if Bit
10 of the DMT entry is set to a 1, then the S/D bit comparison
is considered a match. It is also possible, through DMP
Control Register 1, to enable “All Call Mode” as defined in the
ARINC 429 specification. When enabled for a particular
receive channel, the S/D bits will be considered a match when
the incoming ARINC 429 data contains a 00 in its S/D bit
pair.
3) Receive Channel Number: Bits 12 and 13 of each DMT
entry are compared to the number of the channel which
received the ARINC 429 data.
A Data Match has occurred when all of the previous conditions
are satisfied; the data will then be stored in a RAM location
whose address equals the matching DMT entry minus 200 hex.
Bit 11 of each DMT entry, when set, will cause the incoming
ARINC 429 data to be stored in the corresponding receive chan-
nel FIFO (as well as the Rx RAM) when the data match condi-
tions are met.
Bits 14 and 15 of each DMT entry provide the ability to cause
one of three general purpose interrupts upon a data match con-
dition. If set to “00” then no interrupt will occur upon a data match
condition (more information on interrupts is described later).
ARINC 429 TRANSMITTER(S)
The DD-00429 supports two ARINC 429 transmitters. Each of
these channels transmits data independently and are designated
Tx0 and Tx1. The transmit output of the DD-00429 is a TTL
encoded digital data stream which can be connected directly to
the ARINC 429 line driver.
Transmit Data Rates: Data rates can be programmed for
Channels 0 and 1 independently. The transmit data rate is deter-
mined by the High-Speed/Low-Speed Bit for each of the Tx chan-
nels in Arinc Control Register 1 and the associated ARINC Clock
input (ARINC CLK 0 or ARINC CLK 1). The two, 1 MHz ARINC
clock inputs may be tied to the 1 MHz clock output or they may
be connected to another clock source to achieve transmit data
rates other than 100 kHz or 12.5 kHz. The transmit clock input
should be 10 times (for High-Speed Mode) or 80 times (for Low-
Speed mode) the desired ARINC transmit data rate.
Transmit FIFOs: Each transmitter channel is provided with an
output FIFO which is 32 words deep by 32 bits wide. When writ-
ing data to the Tx FIFO, the associated Disable Tx(n) bit in
ARINC Control Register 2 can be set to a logic zero until the
FIFO is loaded with the desired data. Upon setting the Disable
Tx(n) low the transmit channel will send the 32-bit message
words with appropriate interword gaps on the ARINC 429 output.
A status bit indicating that the FIFO is empty is supplied for each
transmitter in the ARINC Status Register.
Wraparound testing can be performed from Tx0 to Rx0 and Rx1,
and from Tx1 to Rx2 and Rx3. The data received on Rx1 and
Rx3 in wraparound test mode is inverted. Wraparound testing is
enabled by setting the appropriate bits in Arinc Control Register
1. The parity of the transmitted word can be altered to no parity
(instead of the usual odd parity) by setting the associated Tx(n)
Parity bit in the Arinc Control Register 1. This is useful to verify
proper operation of the parity check circuitry for each of the
receive circuits during wraparound test mode.