Functional Description
Furthermore, all enhanced configuration device configuration schemes
(PS, FPP, and concurrent PS) are supported with the page mode feature.
The number of pages and/or devices that can be configured using a
single enhanced configuration device is only limited by the size of the
flash memory.
f
For detailed information on the page mode feature implementation and
programming file generation steps using Quartus II software, refer to
Using Altera Enhanced Configuration Devices, chapter 3 in volume 2 of the
Configuration Handbook.
Real-Time Decompression
Enhanced configuration devices support on-chip real time
decompression of configuration data. FPGA configuration data is
compressed by the Quartus II software and stored in the enhanced
configuration device. During configuration, the decompression engine
inside the enhanced configuration device will decompress or expand
configuration data. This feature increases the effective configuration
density of the enhanced configuration device up to 7, 15, or 30 Mbits in
the EPC4, EPC8, and EPC16, respectively.
The enhanced configuration device also supports a parallel 8-bit data bus
to the FPGA to reduce configuration time. However, in some cases, the
FPGA data transfer time is limited by the flash read bandwidth. For
example, when configuring an APEX II device in FPP (byte-wide data per
cycle) mode at a configuration speed of 66 MHz, the FPGA write
bandwidth is equal to 8 bits × 66 MHz = 528 Mbps. The flash read
interface, however, is limited to approximately 10 MHz (since the flash
access time is ~90 ns). This translates to a flash read bandwidth of
16 bits × 10 MHz = 160 Mbps. Hence, the configuration time is limited by
the flash read time.
When configuration data is compressed, the amount of data that needs to
be read out of the flash is reduced by about 50%. If 16 bits of compressed
data yields 30 bits of uncompressed data, the flash read bandwidth
increases to 30 bits × 10 MHz = 300 Mbps, reducing overall configuration
time.
You can enable the controller's decompression feature in the Quartus II
software, Configuration Device Options window by turning on
Compression Mode.
2–16
Altera Corporation
Configuration Handbook, Volume 2
August 2005
ALTERA [ ALTERA CORPORATION ]
