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INITIALIZATION AND SYSTEM REQUIREMENTS
•
Never apply power to an i960 Jx processor pin or a device connected to an i960 Jx processor
pin before applying power to the i960 Jx processor itself.
•
Prevent overshoot and undershoot on I/O pins by adding line termination and by designing to
reduce noise and reflection on signal lines.
12.6.10
Interference
Interference is the result of electrical activity in one conductor that causes transient voltages to
appear in another conductor. Interference increases with the following factors:
•
Frequency Interference is the result of changing currents and voltages. The more frequent the
changes, the greater the interference.
•
Closeness-of-conductors Interference is due to electromagnetic and electrostatic fields whose
effects are weaker further from the source.
Two types of interference must be considered in high frequency circuits: electromagnetic inter-
ference (EMI) and electrostatic interference (ESI).
EMI is caused by the magnetic field that exists around any current-carrying conductor. The
magnetic flux from one conductor can induce current in another conductor, resulting in transient
voltage. Several precautions can minimize EMI:
•
Run ground lines between two adjacent lines wherever they traverse a long section of the
circuit board. The ground line should be grounded at both ends.
•
Run ground lines between the lines of an address bus or a data bus if either of the following
conditions exist:
-
The bus is on an external layer of the board.
-
The bus is on an internal layer but not sandwiched between power and ground planes
that are at most 10 mils away.
12-40
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