EP2C8T144I8N Datasheet, PDF (363/470 Pages) Altera Corporation – Cyclone II Device Handbook, Volume 1

Altera Corporation
February 2007
Configuring Cyclone II Devices
Reset Stage
When nCONFIG or nSTATUS are low, the device is in reset. After POR, the
Cyclone II device releases nSTATUS. An external 10-kΩ pull-up resistor
pulls the nSTATUS signal high, and the Cyclone II device enters
configuration mode.
1
V_CCINT and V_CCIO of the banks where the configuration and
JTAG pins reside need to be fully powered to the appropriate
voltage levels in order to begin the configuration process.
Configuration Stage
The serial clock (DCLK) generated by the Cyclone II device controls the
entire configuration cycle and provides the timing for the serial interface.
Cyclone II devices use an internal oscillator to generate DCLK. Using the
MSEL[] pins, you can select either a 20- or 40-MHz oscillator. Although
you can select either 20- or 40-MHz oscillator when designing with serial
configuration devices, the 40-MHz oscillator provides faster
configuration times. There is some variation in the internal oscillator
frequency because of the process, temperature, and voltage conditions in
Cyclone II devices. The internal oscillator is designed such that its
maximum frequency is guaranteed to meet EPCS device specifications.
Table 13–5 shows the AS DCLK output frequencies.
Table 13–5. AS DCLK Output Frequency Note (1)
Oscillator Selected
40 MHz
20 MHz
Minimum
20
10
Typical
26
13
Maximum
40
20
Note to Table 13–5:
(1) These values are preliminary.
Units
MHz
MHz
In both AS and Fast AS configuration schemes, the serial configuration
device latches input and control signals on the rising edge of DCLK and
drives out configuration data on the falling edge. Cyclone II devices drive
out control signals on the falling edge of DCLK and latch configuration
data on the falling edge of DCLK.
In configuration mode, the Cyclone II device enables the serial
configuration device by driving its nCSO output pin low, which connects
to the chip select (nCS) pin of the configuration device. The Cyclone II
device uses the serial clock (DCLK) and serial data output (ASDO) pins to
send operation commands and/or read address signals to the serial
13–9
Cyclone II Device Handbook, Volume 1