10. Hot-Socketing and Power-On Reset in
the Cyclone III Device Family
July 2012
CIII51011-3.4
CIII51011-3.4
The Cyclone® III device family (Cyclone III and Cyclone III LS devices) offers
hot-socketing, which is also known as hot plug-in or hot swap, and power sequencing
support without the use of any external devices. You can insert or remove Cyclone III
device family or a board in a system during system operation without causing
undesirable effects to the running system bus or the board that is inserted into the
system.
The hot-socketing feature removes some of the difficulties that you encounter when
you use Cyclone III device family on a PCB that contains a mixture of 3.3, 3.0, 2.5, 1.8,
1.5, and 1.2 V devices. With the hot-socketing feature of Cyclone III device family, you
no longer need to ensure a proper power up sequence for each device on the board.
Cyclone III device family hot-socketing feature provides:
■
Board or device insertion and removal without external components or board
manipulation
■
■
Support for any power-up sequence
Non-intrusive I/O buffers to system buses during hot insertion
This chapter also describes the power-on reset (POR) circuitry in Cyclone III device
family. The POR circuitry keeps the devices in the reset state until the power supplies
are in operating range.
This chapter contains the following sections:
■
■
■
“Hot-Socketing Specifications” on page 10–1
“Hot-Socketing Feature Implementation” on page 10–3
“POR Circuitry” on page 10–3
Hot-Socketing Specifications
Cyclone III device family is a hot-socketing compliant without the need for any
external components or special design requirements. Hot-socketing support in
Cyclone III device family has the following advantages:
■
You can drive the device before power-up without damaging the device.
■
I/O pins remain tristated during power-up. The device does not drive out before
or during power-up, therefore not affecting other buses in operation.
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Cyclone III Device Handbook
Volume 1
July 2012
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