HI-3588
FUNCTIONAL DESCRIPTION (cont.)
ARINC 429 RECEIVER
ARINC BUS INTERFACE
Figure 1 shows the input circuit for the ARINC 429 line receiver. The
ARINC 429 specification requires the following detection levels:
STATE
ONE
NULL
ZERO
DIFFERENTIAL VOLTAGE
+6.5 Volts to +13 Volts
+2.5 Volts to -2.5 Volts
-6.5 Volts to -13 Volts
RINA-40
RINA
VDD
DIFFERENTIAL
AMPLIFIERS
COMPARATORS
ONE
RINB
RINB-40
GND
VDD
GND
FIGURE 1. ARINC RECEIVER INPUT
NULL
ZERO
The HI-3588 guarantees recognition of these levels with a common
mode voltage with respect to GND less than ±30V for the worst case
condition (3.15V supply and 13V signal level). Design tolerances
guarantee detection of the above levels, so the actual acceptance
ranges are slightly larger. If the ARINC signal (including nulls) is
outside the differential voltage ranges, the HI-3588 receiver rejects
the data.
RECEIVER LOGIC OPERATION
Figure 2 is a block diagram showing receiver logic.
BIT TIMING
The ARINC 429 specification defines the following timing toler-
ances for received data:
The HI-3588 accepts signals within these tolerances and rejects
signals outside these tolerances. Receiver logic achieves this as
described below:
1. An accurate 1MHz clock source is required to validate the
receive signal timing. Less than 1% error is recommended.
2. The receiver uses three separate 10-bit sampling shift reg-
isters for Ones detection, Zeros detection and Null detection.
When the input signal is within the differential voltage range
for any shift register’s state (One Zero or Null) sampling
clocks a high bit into that register. When the receive signal is
outside the differential voltage range defined for any shift reg-
ister, a low bit is clocked. Only one shift register can clock a
high bit for any given sample. All three registers clock low
bits if the differential input voltage is between defined state
voltage bands.
Valid data bits require at least three consecutive One or Zero
samples (three high bits) in the upper half of the Ones or Ze-
ros sampling shift register, and at least three consecutive Null
samples (three high bits) in the lower half of the Null sampling
shift register within the data bit interval.
A word gap Null requires at least three consecutive Null sam-
ples (three high bits) in the upper half of the Null sampling
shift register and at least three consecutive Null samples
(three high bits) in the lower half of the Null sampling shift reg-
ister. This guarantees the minimum pulse width.
3. To validate the receive data bit rate, each bit must follow
its preceding bit by not less than 8 samples and not more
than 12 samples. With exactly 1MHz input clock frequency,
the acceptable data bit rates are:
DATA BIT RATE MIN
DATA BIT RATE MAX
HIGH SPEED LOW SPEED
83K BPS
125K BPS
10.4K BPS
15.6K BPS
4. Following the last data bit of a valid reception, the Word
Gap timer samples the Null shift register every 10 input
clocks (every 80 clocks for low speed). If a Null is present,
the Word Gap counter is incremented. A Word Gap count of 3
enables the next reception.
BIT RATE
PULSE RISE TIME
PULSE FALL TIME
PULSE WIDTH
HIGH SPEED
100K BPS ± 1%
1.5 ± 0.5 µsec
1.5 ± 0.5 µsec
5 µsec ± 5%
LOW SPEED
12K -14.5K BPS
10 ± 5 µsec
10 ± 5 µsec
34.5 to 41.7 µsec
HOLT INTEGRATED CIRCUITS
5