HI-8785(2001) View Datasheet(PDF) - Holt Integrated Circuits
Part Name
Description
MFG CO.
HI-8785
(Rev.:2001)
(Rev.:2001)
Holt Integrated Circuits
HI-8785 Datasheet PDF : 9 Pages
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HI-8783, HI-8784, HI-8785
PIN DESCRIPTIONS
PIN
PIN
PIN SYMBOL FUNCTION
HI-8783 HI-8783 HI-8784
(20-pin) (22-pin) HI-8785
DESCRIPTION
1
2
3-10
11
12
-
13
14
15
16
17
-
18
19
-
-
20
-
22
1
2-8,10
11
12
-
14
15
16
17
18
-
19
20
-
-
21
-
1
2
3-9,11
12
13
14
15
16
17
18
19
20
-
-
21
22
23
24
VCC
power supply +5 volt rail,
561 SYNC digital output ARINC 561 Sync signal
Dn
digital inputs Parallel 8 bit Data Input
GND power supply Ground
A0
digital input Byte address, A0=1 for 1st byte, A0=0 for 2nd, 3rd & 4th bytes
SLP1.5 digital input Selects the slope of the line driver. High = 1.5us
WRITE digital input Write strobe, loads data on rising edge
RESET digital input Registers and sequencing logic initialized when low
XMIT CLK digital input Clock input for the transmitter
XMT RDY digital output Goes high if the buffer register is empty
PARITY ENB digital input When high the 32nd bit output is odd parity
V-
power supply -10 volt rail
DATA ONE digital output Goes high for each ARINC bit output that is a “one”
DATA ZERO digital output Goes high for each ARINC bit output that is a “zero”
TXAOUT analog output Line driver ouptut - A side
TXBOUT analog output Line driver output - B side
561 DATA digital output Serial output for ARINC 561 data
V+
power supply +10 volt rail
FUNCTIONAL DESCRIPTION
The HI-8783 is a parallel to serial converter, which when
loaded with four eight bit parallel bytes, outputs the data as
a 32 bit serial word. Timing circuitry inserts a 4 bit gap at the
end of each 32 bit word. An input buffer register allows load
operations to take place while the previously loaded word
is being transmitted.
If the PARITY ENB pin is high, the 32nd bit will be a parity
bit, inserted so as to make the 32 bit word have odd parity. If
the PARITY ENB pin is low, the 32nd bit will be the D7 bit of
the 4th byte.
Outputs are provided for both ARINC 429/575 (DATA ONE
and DATA ZERO pins), and ARINC 561 (561 DATA and
561 SYNC pins) type data.
Input data can be loaded when the XMT RDY signal is
high, which indicates the input buffer register is empty. The
first 8 bit byte is the label byte and is loaded with the A0 in-
put high, which initializes the internal byte counter. The re-
maining three bytes are loaded with A0 in the low state.
Each 8 bit byte is loaded into the input buffer register by a
low pulse on the WRITE input. (See figure 1). After the
fourth byte is loaded, the XMT RDY output goes low. The
contents of the input buffer register are transferred to the
output register during the fourth bit period of the gap. If the
fourth gap bit period of the previous word has already been
transmitted, the contents of the input buffer register will be
transferred to the output shift register during the first bit pe-
riod after the loading of the fourth byte, and the XMT RDY
output goes high.
A low signal applied to the RESET pin resets the HI-8783’s
internal logic so that spurious transmission does not take
place during power-up. The registers are cleared so that a
continuous gap will be transmitted until the first word is
loaded into the transmitter.
After the output shift register is loaded, the data is shifted
out to the output logic in the order shown in figure 2.
The 561 SYNC output pulses low when the XMT CLK is low
during the 8th bit of the ARINC transmission.
The XMIT CLK is the same as the data rate.
HOLT INTEGRATED CIRCUITS
2
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