FS2003 ISP
Programmer - User Guide V1.07 – 1
st
September 2007
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2.7 Earthing requirements
2.7.1 Overview
When setting up the programmer to In-System Program (ISP) a device on a Target System, extreme
care must be taken to ensure that the 0V of the PC, programmer, Target System and any external
devices are at the same ‘earth potential’. If you are using the programmer with a laptop computer,
please read section 3.2.2 carefully.
ESD Points to remember
Failure to follow correct ESD procedures when using this product could lead to
damage to the programmer and/or the Target System.
•
Wear an earthed wrist strap when handling either the programmer and/or
any programmable device.
•
Ensure that the PC, programmer, Target System and any external devices
are all connected to the same GROUND potential.
2.7.2 Laptop earthing issues
The Problem:
Most laptops use an external double-insulated mains power supply which is not earthed to mains
earth. This means that the laptop earth is likely to be floating at some voltage other than 0V. If the
programmer is attached to the PC COM port with the PC powered ON and then the ISP lead is
plugged into an earthed Target System, then the PC GROUND will discharge through the COM port
GROUND, through the programmer into the Target System. This ESD may damage both the
programmer and the Target System !
The Solution
•
Ensure that the laptop is powered OFF when connecting the ISP cable from the programmer
to an earthed Target system
•
Use the programmer in
Standalone Mode
if possible (ie. not connected to a PC)
2.7.3 Desktop PC earthing issues
The Problem:
The chassis on desktop PC must be connected to mains earth to comply with Health and Safety
legislation. If the chassis is not earthed for some reason, the PC power supply GROUND will be
floating and it is then possible to discharge a high level of energy stored in the power supply mains
filter through the programmer into the Target System. This ESD may damage both the programmer
and the Target System !
The solution:
•
Ensure that the PC chassis is properly earthed to mains earth.
•
Connect an earthing bond wire from the PC chassis to the GROUND connection of either the
programmer or the Target system / Test Fixture.
