HIP7020 Datasheet, PDF (9/11 Pages) Intersil Corporation – J1850 Bus Transceiver For Multiplex Wiring Systems

HIP7020
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
The R/F (Rise/Fall) Time pin connects the external resistor, R_S,
from the wave shaped voltage reference to ground. The Rise
and Fall Time is controlled by the transition slope of the signal
waveform. The resistor, R_S, sets an internal current reference
to control the rise and fall slope. As previously noted, the resis-
tor, R_S, should be located as close as possible to the IC to min-
imize noise coupling to the R/F pin. Also, the ground connection
of R_S must be made directly to the GND pin of the IC with no
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
through an external Resistor, R_F.
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.
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