FUNCTIONAL DESCRIPTION (cont.)

LINE DRIVER OPERATION

The line driver in the HI-8599 is designed to directly drive the

ARINC 429 bus.

The two ARINC outputs (TXA(OUT) and

TXB(OUT)) provide a differential voltage to produce a +10 volt

One, a -10 volt Zero, and a 0 volt Null. Setting Control Register bit

13 to zero causes a slope of 1.5 s on the ARINC outputs. A one in

Control Register bit 13 causes a slope of 10 s. Timing is set by on-

chip resistor and capacitor and tested to be within ARINC require-

ments.

he

HI-8599 has 10 ohms in series with each line driver output, and is

for applications where additional external series resistance is

required, such as lightning protection.

m

m

No additional hardware is required to control the slope. T

Repeater mode of operation allows a data word that has been

received by the HI-8599 to be placed directly into its FIFO for

transmission.

Repeater operation is similar to normal receiver

operation. In normal operation, either byte of a received data word

may be read from the receiver latches first by use of SEL input.

During repeater operation however, the lower byte of the data word

must be read first. This is necessary because, as the data is being

read, it is also being loaded into the FIFO and the transmitter FIFO

is always loaded with the lower byte of the data word first. Signal

flow for

repeater operation is shown in the Timing Diagrams

section.

REPEATER OPERATION

DATA RATE - EXAMPLE PATTERN

TXA(OUT)

ARINC BIT

TXB(OUT)

NULL

DATA

DATA

DATA

NULL

NULL

WORD GAP

BIT 1

NEXT WORD

BIT 32

BIT 31

BIT 30

LOADING CONTROL WORD

CWHLD

t

CWSET

t

CWSTR

t

DATA BUS

CWSTR

VALID

TIMING DIAGRAMS

HI-8599

HI-8599-10

The “-10” version of the HI-8599 product require a 10 Kohm

resistor to be placed in series with each ARINC input without

affecting the ARINC input thresholds. This option is especially

useful in applications where external lightning protection is

required.

Each ARINC input pin must be connected to the ARINC bus

through a 10 Kohm resistor in order for the chip to properly detect

the correct ARINC levels. The typical 10 volt differential signal is

translated and input to a window comparator and latch.

The

comparator levels are set so that with the external 10 Kohm

resistors, they are just below the standard 6.5 volt minimum

ARINC data threshold and just above the 2.5 volt

maximum

ARINC null threshold.

Please refer to the Holt AN-300 Application Note for additional

information and recommendations on lightning protection of Holt

line drivers and line receivers.

POWER SUPPLY SEQUENCING

The power supplies should be controlled to prevent large currents

during supply turn-on and turn-off. The recommended sequence

is V+ followed by Vcc, always ensuring that V+ is the most

positive supply. The V- supply is not critical and can be asserted

at any time.

HOLT INTEGRATED CIRCUITS

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