EP3C80 datasheet(167/274 Pages) ALTERA

167 / 274 page

Chapter 9: Configuration, Design Security, and Remote System Upgrades in the Cyclone III Device Family

9–9

Configuration Features

August 2012

Altera Corporation

Cyclone III Device Handbook

Volume 1

When the device exits POR, all user I/O pins continue to tri-state. The user I/O pins

and dual-purpose I/O pins have weak pull-up resistors that are always enabled (after

POR) before and during configuration. After POR, the Cyclone III device family

releases nSTATUS, which is pulled high by an external 10-k pull-up resistor and

enters configuration mode.

When nCONFIG goes high, the device exits reset and releases the open-drain nSTATUS

pin, which is then pulled high by an external 10-kpull-up resistor. After nSTATUS is

released, the device is ready to receive configuration data and the configuration stage

begins.

Cyclone III LS devices are accessible by limited JTAG instructions after POR. For more

information about enabling full JTAG instructions access, refer to “JTAG Instructions”

on page 9–60.

f For more information about the value of weak pull-up resistors on the I/O pins that

are on before and during configuration, refer to the Cyclone III Device Data Sheet and

Cyclone III LS Device Data Sheet chapters.

Configuration

Configuration data is latched into the Cyclone III device family at each DCLK cycle.

However, the width of the data bus and the configuration time taken for each scheme

are different. After the device receives all the configuration data, the device releases

the open-drain CONF_DONE pin, which is pulled high by an external 10-kpull-up

resistor. A low-to-high transition on the CONF_DONE pin indicates that configuration is

complete and initialization of the device can begin. The CONF_DONE pin must have an

external 10-k pull-up resistor for the device to initialize.

You can begin reconfiguration by pulling the nCONFIG pin low. The nCONFIG pin must

be low for at least 500 ns. When nCONFIG is pulled low, the Cyclone III device family is

reset. The Cyclone III device family also pulls nSTATUS and CONF_DONE low and all I/O

pins are tri-stated. When nCONFIG returns to a logic-high level and nSTATUS is released

by the Cyclone III device family, reconfiguration begins.

Configuration Error

If an error occurs during configuration, the Cyclone III device family asserts the

nSTATUS

signal low, indicating a data frame error, and the CONF_DONE signal stays low.

If the Auto-restart configuration after error option (available in the Quartus II

software from the General tab of the Device and Pin Options dialog box) is turned

on, the Cyclone III device family releases nSTATUS after a reset time-out period (a

maximum of 230 s), and retries configuration. If this option is turned off, the system

must monitor nSTATUS for errors and then pulse nCONFIG low for at least 500 ns to

restart configuration.

EP3C80 Datasheet(PDF) 167 Page - Altera Corporation

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