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Functional Description
For example, if your system requires three configuration pages and includes two
FPGAs, each page will store two SRAM Object Files (.sof) for a total of six .sof in the
configuration device.
Furthermore, all EPC device configuration schemes (PS, FPP, and concurrent PS) are
supported with the page-mode feature. The number of pages, devices, or both, that
can be configured using a single EPC device is only limited by the size of the flash
memory.
f For more information about the page-mode feature implementation and
programming file generation steps using the Quartus II software, refer to the Altera
Enhanced Configuration Devices.
Real-Time Decompression
EPC devices support on-chip real time decompression of configuration data. FPGA
configuration data is compressed by the Quartus II software and stored in the EPC
device. During configuration, the decompression engine inside the EPC device will
decompress or expand configuration data. This feature increases the
effective-configuration density of the EPC device up to 7, 15, or 30 Mb in the EPC4,
EPC8, and EPC16 devices, respectively.
The EPC 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.
1
The decompression feature supported in the EPC devices is different from the
decompression feature supported by the Stratix II FPGAs and the Cyclone series.
When configuring Stratix II FPGAs or the Cyclone series using EPC devices, Altera
recommends enabling decompression in Stratix II FPGAS or the Cyclone series only
for faster configuration.
The compression algorithm used in Altera devices is optimized for FPGA
configuration bitstreams. Since FPGAs have several layers of routing structures (for
high performance and easy routability), large amounts of resources go unused. These
unused routing and logic resources as well as un-initialized memory structures result
in a large number of configuration RAM bits in the disabled state. Altera's proprietary
compression algorithm takes advantage of such bitstream qualities.
Enhanced Configuration (EPC) Devices Datasheet
January 2012 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
