9–14
Chapter 9: Configuration, Design Security, and Remote System Upgrades in the Cyclone III Device Family
Configuration Features
In a single-device AS configuration, the maximum board loading and board trace
length between the supported serial configuration device and the Cyclone III device
family must follow the recommendations in Table 9–9 on page 9–20.
The DCLKgenerated by the Cyclone III device family controls the entire configuration
cycle and provides timing for the serial interface. Cyclone III device family uses a 40-
MHz internal oscillator to generate DCLK. There are some variations in the internal
oscillator frequency because of the process, voltage, and temperature conditions in
Cyclone III device family. The internal oscillator is designed to ensure that its
maximum frequency is guaranteed to meet the EPCS device specifications.
1
EPCS1 does not support Cyclone III device family because of its insufficient memory
capacity.
Table 9–8 lists the AS DCLKoutput frequency for Cyclone III device family.
Table 9–8. AS DCLK Output Frequency
Oscillator
Minimum
Typical
Maximum
Unit
40 MHz
20
30
40
MHz
In the AS configuration scheme, the serial configuration device latches input and
control signals on the rising edge of DCLKand drives out configuration data on the
falling edge. Cyclone III device family drives out control signals on the falling edge of
DCLKand latch configuration data on the falling edge of DCLK
.
In configuration mode, the Cyclone III device family enables the serial configuration
device by driving the nCSOoutput pin low, which connects to the nCSpin of the
configuration device. The Cyclone III device family uses the DCLKand DATA[1]pins to
send operation commands and read address signals to the serial configuration device.
The configuration device provides data on its DATApin, which connects to the DATA[0]
input of the Cyclone III device family.
After all the configuration bits are received by the Cyclone III device family, it releases
the open-drain CONF_DONEpin, which is pulled high by an external 10-k resistor.
Initialization begins only after the CONF_DONEsignal reaches a logic-high level. All AS
configuration pins (DATA[0], DCLK, nCSO, and DATA[1]) have weak internal pull-up
resistors that are always active. After configuration, these pins are set as input tri-
stated and are driven high by weak internal pull-up resistors. The CONF_DONEpin must
have an external 10-k pull-up resistor for the device to initialize.
The timing parameters for AS mode are not listed here because the tCF2CD, tCF2ST0, tCFG
STATUS, tCF2ST1, and tCD2UM timing parameters are identical to the timing parameters
,
t
for PS mode listed in Table 9–13 on page 9–39.
Multi-Device AS Configuration
You can configure multiple Cyclone III device family using a single serial
configuration device. You can cascade multiple Cyclone III device family using the
chip-enable (nCE) and chip-enable-out (nCEO) pins. The first device in the chain must
have its nCEpin connected to GND. You must connect its nCEOpin to the nCEpin of the
next device in the chain. Use an external 10-k pull-up resistor to pull the nCEOsignal
high to its VCCIO level to help the internal weak pull-up resistor. When the first device
Cyclone III Device Handbook
Volume 1
August 2012 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
