EP3C80 datasheet(178/274 Pages) ALTERA

178 / 274 page

9–20

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

Configuration Features

Cyclone III Device Handbook

August 2012

Altera Corporation

Volume 1

Altera recommends putting a buffer before the DATA and DCLK output from the master

device to avoid signal strength and integrity issues. The buffer must not significantly

change the DATA-to-DCLK relationships or delay them with respect to other AS signals

(ASDI and nCS). Also, the buffer must only drive the slave devices to ensure that the

timing between the master device and the serial configuration device is unaffected.

This configuration method supports both compressed and uncompressed .sofs.

Therefore, if the configuration bitstream size exceeds the capacity of a serial

configuration device, you can enable the compression feature in the .sof or you can

select a larger serial configuration device.

Guidelines for Connecting Serial Configuration Device to Cyclone III Device

Family on AS Interface

For single- and multi-device AS configurations, the board trace length and loading

between the supported serial configuration device and Cyclone III device family must

follow the recommendations listed in Table 9–9.

Estimating AS Configuration Time

AS configuration time is dominated by the time it takes to transfer data from the serial

configuration device to the Cyclone III device family. This serial interface is clocked

by the Cyclone III device family DCLK output (generated from an internal oscillator).

Equation 9–2 and Equation 9–3 show the configuration time estimation for the

Cyclone III device family.

To estimate the typical configuration time, use the typical DCLK period shown in

Figure 9–7 on page 9–22. With a typical DCLK period of 33.33 ns, the typical

configuration time is 116.7 ms. Enabling compression reduces the amount of

configuration data that is sent to the Cyclone III device family, which also reduces

configuration time. On average, compression reduces configuration time by 50%.

Table 9–9. Maximum Trace Length and Loading for the AS Configuration

Cyclone III

Device Family

AS Pins

Maximum Board Trace Length from the

Cyclone III Device Family to the Serial

Configuration Device (Inches)

Maximum Board Load (pF)

DCLK

DATA[0]

nCSO

ASDO

Equation 9–2.

Equation 9–3.

Size

maximum DCLK period

1 bit

----------------------------------------------------------------







estimated maximum configuration ti

3,500,000 bits

50 ns

1 bit

-------------







175 ms

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