HI-8685, HI-8686
December 2008
ARINC INTERFACE DEVICE
ARINC 429 & 561 Serial Data to 16-Bit Parallel Data
PIN CONFIGURATIONS
(Top View)
DATARDY
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
Vcc
GAPCLK
TESTA
TESTB
RESET
RINB (-10)
RINA (-10)
ERROR
PARITY ENB
READ
D0
D1
D2
D3
DESCRIPTION
The HI-8685 and HI-8686 are system components for
interfacing incoming ARINC 429 signals to 16-bit parallel
data using proven +5V analog/digital CMOS technology.
Both products incorporate the digital logic and analog line
receiver circuitry in a single device.
The receivers on the HI-8685 and the HI-8686 connect
directly to the ARINC 429 Bus and translate the incoming
signals to normal CMOS levels. Internal comparator levels
are set just below the standard 6.5 volt minimum data
threshold and just above the standard 2.5 volt maximum null
threshold. The -10 version of the HI-8685 allows the
incorporation of an external 10K
W
resistance in series with
each ARINC input for lightning protection without affecting
ARINC level detection.
Both products offer high speed 16-bit parallel bus interface,
a 32-bit buffer, and error detection for word length and parity.
A reset pin is also provided for power-on initialization.
HI-8685PSI
23
HI-8685PST
22
&
21
HI-8685PSI-10
HI-8685PST-10
20
19
18
17
16
15
FEATURES
!
Automatic conversion of serial ARINC 429, 575 &
561 data to 16-bit parallel data
HI-8685
28-Pin Plastic SOIC - WB Package
29 - DATARDY
27 - GAPCLK
!
!
!
!
!
!
!
Error detection - word length and parity
Reset input for power-on initialization
On-chip line receiver
Input hysteresis of at least 2 volts
Test lnputs bypass analog inputs
Simplified lightning protection with the ability to
add 10 Kohm external series resistors
SOIC, PQFP and PLCC
N/C - 1
D12 - 2
D11 - 3
D10 - 4
D9 - 5
D8 - 6
D7 - 7
D6 - 8
28 - Vcc
High speed parallel 16-bit data bus
25 - TESTB
26 - TESTA
32 - D13
31 - D14
30 - D15
24 - RESET
23 - RINB-10
22 - RINB
21 - RINA
20 - RINA-10
19 - ERROR
18 - PARITY ENB
17 - N/C
HI-8686PQI
HI-8686PQT
!
Small, surface mount, plastic package options:
!
Industrial and extended temperature ranges
D4 - 10
D3 - 12
D2 - 13
D1 - 14
D0 - 15
APPLICATIONS
!
Avionics data communication
!
Serial to parallel conversion
!
Parallel to serial conversion
HI-8686
32-Pin Plastic PQFP Package
(See page 8 for additional pin configurations)
(DS8685 Rev. N)
HOLT INTEGRATED CIRCUITS
www.holtic.com
READ - 16
GND - 11
D5 - 9
12/08
HI-8685, HI-8686
PIN DESCRIPTIONS
SIGNAL
DATA RDY
D0 to D15
GND
READ
PARITY ENB
ERROR
FUNCTION
OUTPUT
OUTPUT
POWER
INPUT
INPUT
OUTPUT
DESCRIPTION
Receiver data ready flag. A high level indicates data is available in the receive
buffer. Flag goes low when the first 16-bit byte is read.
16-bit parallel data bus (tri-state)
0V
Read strobe. A low level transfers receive buffer data to the data bus
Parity Enable - A high level activates odd parity checking which replaces the
32nd ARINC bit with an error bit. Otherwise, the 32nd ARINC bit is unchanged
Error Flag. A high level indicates a bit count error (number of ARINC bits was
less than or greater than 32) and/or a parity error if parity detection was enabled
(PARITY ENB high)
Positive direct ARINC serial data input (both RINA and RINA-10 on HI-8686)
Negative direct ARINC serial data input (both RINB and RINB-10 on HI-8686)
Internal logic states are initialized with a low level
Used in conjunction with the TESTB input to bypass the built-in analog line
receiver circuitry
Used in conjunction with the TESTA input to bypass the built-in analog line
receiver circuitry
Gap Clock. Determines the minimum time required between ARINC words for
detection. The minimum word gap time is between 16 and 17 clock cycles of
this signal.
+5V ±5% supply
RINA/RINA-10
RINB/RINB-10
RESET
TESTA
TESTB
GAPCLK
INPUT
INPUT
INPUT
INPUT
INPUT
INPUT
Vcc
POWER
FUNCTIONAL DESCRIPTION
The HI-8685 and HI-8686 are serial to 16-bit parallel con-
verters. The incoming data stream is serially shifted into an
input register, checked for errors, and then transferred in par-
allel to a 32-bit receive buffer. The receive data can be ac-
cessed using two 16-bit parallel read operations while the
next serial data steam is being received.
RECEIVER INPUTS
The block diagram for both the HI-8685 and HI-8685-10
products is found in Figure 1. Both have built-in receivers
eliminating the need for additional external ARINC level de-
tection circuitry. The only difference between the two prod-
ucts is the amount of internal resistance in series with each
ARINC input.
HI-8685 ARINC INPUTS (RINA & RINB)
translation, the buffered inputs drive a differential amplifier.
The differential signal is compared to levels derived from a
divider between VCC and GND. The nominal settings cor-
respond to a One/Zero amplitude of 6.0V and a Null ampli-
tude of 3.3V. A valid ARINC One/Zero input sets a latch and
a Null input resets the latch.
HI-8685-10 ARINC INPUTS (RINA-10 & RINB-10)
Since any added external series resistance will affect the
voltage translation, the HI-8685-10 product has only 25K
W
of the 35K
W
series resistance required for proper ARINC
429 level detection. The remaining 10K
W
required is avail-
able to the user for incorporation in external circuitry such as
for lightning protection.
HI-8686 ARINC INPUTS
Internal 35K
W
resistors are in series with both the RINA and
RINB ARINC 429 inputs. They connect to level translators
whose resistance to GND is typically 10K
W.
After level
The HI-8686 has both sets of ARINC inputs, RINA/RINA-10
and RINB/RINB-10 available to the user.
HOLT INTEGRATED CIRCUITS
2
HI-8685, HI-8686
PARITY
ENB
CLK
PARITY
DETECT
10KW
25KW
ESD
PROTECTION
&
LINE
RECEIVER
RXA
ERROR
DETECT
ERROR
RINA
RINB
10KW
25KW
RXB
CLOCK
&
DATA
DETECT
BIT 32
BIT 32
DATA
32-BIT
SHIFT
REG.
32
32-BIT
RECEIVE 32
BUFFER
32-BIT
TO
16-BIT 16
MUX
D0 - D15
RINA-10
RINB-10
TESTA
TESTB
BIT
COUNT
GAP
DETECT
BYTE
COUNT
DATA RDY
GAPCLK
RESET
READ
Figure 1. Block Diagram
FUNCTIONAL DESCRIPTION (cont.)
PROTOCOL DETECTION
The ARINC clock and One/Zero data that are derived from
the digital outputs of the built-in line receiver is illustrated in
Figure 3. The resulting steam of digital data is shifted into a
32-bit input register.
The ARINC clock and One/Zero data can also be created
from the TESTA and TESTB inputs as shown in Figure 4.
When either test input is high, the built-in analog line driver
is disabled.
For ARINC 561 operation, the TESTA and TESTB digital in-
put data streams must be derived from the ARINC 561 data,
clock and sync with external logic.
DATABUS
TYPE
429
BIT PERIOD
(µs)
10
MINIMUM GAP
(µs)
45
GAP CLOCK
MHz
0.75
1.0
1.5
0.1
0.1
0.2
GAP DETECTION
TIME (µs)
21.3 - 22.7
16 - 17
10.7 - 11.3
160 - 170
160 - 170
80 - 85
GAP DETECTION
The end of a data word is detected by an internal counter
that times out when a data One or Zero is not received for a
period equal to 16 cycles of the GAPCLK signal. The gap
detection time may vary between 16 and 17 cycles of the
GAPCLK signal since the incoming data and GAPCLK are
not usually synchronous inputs. The required frequency of
GAPCLK is a function of the mininum gap time specified for
the type of ARINC data being received. Table 1 indicates
typical frequencies that may be used for the various data
rates normally encountered.
429
575
561
69 - 133
69 - 133
69 - 133
310 - 599
310 - 599
103 - 200
Table 1 - Typical Gap Detection Times
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HI-8685, HI-8686
FUNCTIONAL DESCRIPTION (cont.)
ERROR CHECKING
Once a word gap is detected, the data word in the input
register is transferred to the receive buffer and checked
for errors.
When parity detection is enabled (PARITY ENB high), the
received word is checked for odd parity. If there is a parity
error, the 32nd bit of the received data word is set high.
If parity checking is disabled (PARITY ENB low) the 32nd
bit of the data word is always the 32nd ARINC bit re-
ceived.
The ERROR flag output is set high upon receipt of a word
gap and the number of bits received since the previous
word gap is less than or greater than 32. The ERROR flag
is reset low when the next valid ARINC word is written into
the receive buffer or when RESET is pulsed low.
READING RECEIVE BUFFER
When the data word is transferred to the receive buffer,
the DATA RDY pin goes high. The data word can then be
read in two 16-bit bytes by pulsing the READ input low as
indicated in Figure 5. The first read cycle resets
DATARDY low and increments an internal counter to the
second 16-bit byte. The relationship between each bit of
an ARINC word received and each bit of the two 16-bit
data bus bytes is specified in Figure 2.
When a new ARINC word is received it always overwrites
the receive buffer. If the first byte of the previous word
has not been read, then previous data is lost and the
receive buffer will contain the new ARINC word. How-
ever, if the DATARDY pin goes high between the reading
of the first and second bytes, the first byte is no longer
valid because the corresponding second byte has been
overwritten by the new ARINC word. Also, the next read
will be of the first byte of the new ARINC word since the
internal byte counter is always reset to the first byte when
new data is transferred to the receive buffer.
Read
1st
2nd
Byte
Byte 1
Byte 2
Data Bus Bits
D0 - D15
D0 - D15
ARINC Bits
ARINC 1 - ARINC 16
ARINC 17 - ARINC 32
FIGURE 2. ORDER OF RECEIVED DATA
RESET
A low on the RESET input sets a flip-flop which initializes
the internal logic. When RESET goes high, the internal
logic remains in the initialized state until the first word gap
is detected preventing reception of a partial word.
TEST MODE
The built-in differential line receiver can be disabled allow-
ing the data and clock detection circuitry to be driven di-
rectly with digital signals. The logical OR function of the
TESTA and TESTB is defined in Truth Table 1. The two in-
puts can be used for testing the receiver logic and for input-
ting ARINC 429 type data derived from another source / pro-
tocol. See Figure 4 for typical test input timing.
The device should always be initialized with RESET imme-
diately after entering the test mode to clear a partial word
that may have been received since the last word gap. Oth-
erwise, an ERROR condition may occur and the first 32 bits
of data on the test inputs may not be properly received.
Also, when entering the test mode, both TESTA and
TESTB should be set high and held in that state for at least
one word gap period (17 gap clocks) after RESET goes
high.
When exiting the test mode, both test inputs should be held
low and the device initialized with RESET.
TRUTH TABLE 1.
RINA (-10)
-1.50V to +1.50V
-3.25V to -6.50V
+3.25V to +6.50V
X
X
X
X = don't care
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4
RINB (-10)
-1.50V to +1.50V
+3.25V to +6.50V
-3.25V to -6.50V
X
X
X
TESTA
0
0
0
0
1
1
TESTB
0
0
0
1
0
1
RXA
0
0
1
0
1
0
RXB
0
1
0
1
0
0
HI-8685, HI-8686
TIMING DIAGRAMS
28
ARINC Data Bits
29
30
31
32
Word Gap
4 Bit Periods Min.
1
2
+10V
0V
-10V
VDIFF
RINA - RINB
DERIVED DATA
DERIVED CLOCK
FIGURE 3 - RECEIVER INPUT TIMING FOR ARINC 429
28
ARINC Data Bits
29
30
31
32
Word Gap
4 Bit Periods Min.
1
2
+5V
0V
+5V
0V
TESTA
TESTB
DERIVED DATA
DERIVED CLOCK
FIGURE 4 - TEST INPUT TIMING FOR ARINC 429
DERIVED DATA
32nd
ARINC bit
t
DRDY
t
RDYCLR
DATA RDY
t
RDPW
READ
t
RD
D0 - D15
VALID
1st 16-bits
t
RR
2nd 16-bits
t
FD
VALID
FIGURE 5 - RECEIVER PARALLEL DATABUS TIMING
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