HI-8783, HI-8784, HI-8785

PIN DESCRIPTIONS

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.

A low signal applied to the

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.

RESET

FUNCTIONAL DESCRIPTION

PIN

PIN

PIN

SYMBOL

FUNCTION

DESCRIPTION

HI-8783 HI-8783

HI-8784

(20-pin) (22-pin)

HI-8785

2

1

2

561 SYNC

digital output

ARINC 561 Sync signal

3-10

2-8,10

3-9,11

Dn

digital inputs

Parallel 8 bit Data Input

11

11

12

GND

power supply Ground

12

12

13

A0

digital input

Byte address, A0=1 for 1st byte, A0=0 for 2nd, 3rd & 4th bytes

-

-

14

SLP1.5

digital input

Selects the slope of the line driver. High = 1.5us

13

14

15

digital input

Write strobe, loads data on rising edge

14

15

16

digital input

Registers and sequencing logic initialized when low

15

16

17

XMIT CLK

digital input

Clock input for the transmitter

16

17

18

XMT RDY

digital output

Goes high if the buffer register is empty

17

18

19

PARITY ENB digital input

When high the 32nd bit output is odd parity

-

-

20

V-

power supply -10 volt rail

18

19

-

DATA ONE

digital output

Goes high for each ARINC bit output that is a “one”

19

20

-

DATA ZERO

digital output

Goes high for each ARINC bit output that is a “zero”

-

-

21

TXAOUT

analog output Line driver ouptut - A side

-

-

22

TXBOUT

analog output Line driver output - B side

20

21

23

561 DATA

digital output

Serial output for ARINC 561 data

-

-

24

V+

power supply +10 volt rail

1

22

1

VCC

power supply +5 volt rail,

WRITE

RESET

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 input high,

which initializes the internal byte counter. The remaining

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

input. 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 out-

put goes high.

After the output shift register is loaded, the data is shifted out

to the output logic in the order shown in figure 2.

Once A0 is

set low, it must not go high until after the fourth byte is loaded.

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.

WRITE

HOLT INTEGRATED CIRCUITS

2