Manual

IQ-INT II IQ Interface
Page 6
Reference Manual
3 Installation
The installation of an IQ-INT II can be divided into two
major parts: Connecting to one or more Crown Bus loops
and connecting to the host computer.
3.1 Connecting to a Crown Bus Loop
The Crown Bus is a serial communication loop designed
to transmit IQ commands and data. As a communication
standard, it is independent of its wiring. This
characteristic allows you to wire a Crown Bus loop with
either fiber optic cabling or with inexpensive twisted-
pair wire, whichever is most appropriate. One IQ System
can have more than one Crown Bus loop, and each
loop must be unbroken for proper operation.
The IQ-INT II supports up to eight Crown Bus loops.
This makes it possible to divide the system into zones,
each with its own loop. Using the IQ-INT II to drive
multiple Crown Bus loops has several advantages and
disadvantages that are listed next.
Multiloop Advantages
• A break in communication in one loop does not
affect other loops.
• Over 250 IQ components of the same model can
be used in a system.
• The same IQ address can be used more than once
(once for each type of unit on each loop).
• Larger areas can often be covered without using
repeaters or fiber optic cabling.
Fig. 3.1 An IQ System with an IQ-INT II
ENABLEDSPI ENABLEDSPI
CROWN BUS LOOP 1
CROWN BUS LOOP 2
RS232/RS422
ENABLE
POWER
ODEP
IOC
SPI
ENABLE
CH1 CH2
OFF
POWER
ODEP
IOC
SPI
ENABLE
CH1 CH2
OFF
POWER
ODEP
IOC
SPI
ENABLE
CH1 CH2
OFF
POWER
ODEP
IOC
SPI
ENABLE
CH1 CH2
OFF
POWER
ODEP
IOC
SPI
ENABLE
CH1 CH2
OFF
POWER
ODEP
IOC
SPI
ENABLE
CH1 CH2
OFF
Single Loop Advantages
• The IQ-INT II can send and receive data slightly
faster using a single loop.
• “Real-time” levels can be displayed for a greater
number of units.
The IQ-INT II is designed to work with inexpensive
twisted-pair wire, so it implements the Crown Bus as a
20-milliamp current loop operating at a baud rate of
38,400. If you want to use fiber optic cabling, contact
Crown’s Technical Support Group for information on the
appropriate transceivers.
Here are some guidelines for twisted-pair wiring:
• A Crown Bus loop must be unbroken to carry
commands and data to and from connected units.
• Never cross-connect Crown Bus loops. Each
Crown Bus loop is an independent serial
communication circuit. A Crown Bus output is
connected to the input of the first IQ component on
the loop. Each unit’s output connects to the next
unit’s input until the loop returns to the interface
where it is connected to the input for the same loop.
• Use twisted-pair wire at least 26 AWG in size. Use
twisted-pair wire with a shield when interference is
a concern. The wire should be of good quality and
should have low capacitance (30 picofarads/foot
or less). In most cases, interference is not a problem
and unshielded wire is a better choice because of