9

TRANSMIT (TX)

The TRANSMIT pin will accept standard CMOS/TTL logic

level input data. Logic level data is input at the TRANSMIT

(TX) pin in a serial format, such as provided by a Intersil

HIP7030A2 J1850 Controller, and is output on the J1850

Bus at the BUS OUT pin. The TX input has an active pull

down current sink to insure that a logic level low will be main-

tained when no signal drive is present.

RECEIVE (RX)

The RX pin is the output for J1850 Bus data and interfaces

to an open collector transistor output driver. The RX digital

data output is inverted from the analog bus data input at the

BUSIN pin. The data from the RX pin is output to a Intersil

HIP7010 Byte Level I/O or a HIP7030A2 J1850 Microcontrol-

ler IC where the 10.4 Kbps VPWM messages from the

J1850 network are decoded.

GROUND

This is the HIP7020 Bus Transceiver IC ground reference for all

the signals which interface to the control logic and the J1850

bus. It is also the ground return path for the BATTERY power

supply to IC.

R/F TIME

from the wave shaped voltage reference to ground. The Rise

and Fall Time is controlled by the transition slope of the signal

to control the rise and fall slope. As previously noted, the resis-

imize noise coupling to the R/F pin. Also, the ground connection

other current flowing in the connecting line.

BUS IN

The BUS IN pin is the receive input of the SAE J1850 Bus

signal. It receives the 10.4kHz VPWM (Variable pulse width

modulated) data from the single wire analog serial bus

BUS OUT

The BUS OUT pin transmits the SAE J1850 10.4kHz VPWM

(Variable Pulse Width Modulated) data to the serial bus.

Data is transmitted to the serial J1850 bus with the same

polarity as the TX input signal.

LB EN

The LB EN Loop-Back Enable pin controls the Diagnostic

Loop-Back Mode Switch function. A logic low on the LB EN

pin connects the output of the Wave Shaped Voltage Refer-

ence to the Bus Receiver and Voltage Comparator while dis-

connecting the filtered input of J1850 Bus. This feature

provides the means to trouble shoot system problems.

HIP7020