11–2
Chapter 11: SEU Mitigation in the Cyclone III Device Family
Configuration Error Detection
The error detection CRC feature in Cyclone III device family puts theory into practice.
In user mode, the error detection CRC feature in Cyclone III device family ensures the
integrity of the configuration data.
Configuration Error Detection
In configuration mode, a frame-based CRC is stored in the configuration data and
contains the CRC value for each data frame.
During configuration, Cyclone III device family calculates the CRC value based on the
frame of data that is received and compares it against the frame CRC value in the data
stream. Configuration continues until either the device detects an error or all the
values are calculated.
For Cyclone III device family, the CRC is computed by the Quartus
®
II software and
downloaded into the device as part of the configuration bit stream. These devices
store the CRC in the 32-bit storage register at the end of the configuration mode.
User Mode Error Detection
Soft errors are changes in a configuration random-access memory (CRAM) bit state
due to an ionizing particle. Cyclone III device family has built-in error detection
circuitry to detect data corruption by soft errors in the CRAM cells.
This error detection capability continuously computes the CRC of the configured
CRAM bits based on the contents of the device and compares it with the
pre-calculated CRC value obtained at the end of the configuration. If the CRCs match,
there is no error in the current configuration CRAM bits. The process of error
detection continues until the device is reset (by setting
nCONFIG
to low).
The Cyclone III device family error detection feature does not check memory blocks
and I/O buffers. These device memory blocks support parity bits that are used to
check the contents of memory blocks for any error. The I/O buffers are not verified
during error detection because the configuration data uses flip-flops as storage
elements that are more resistant to soft errors. Similar flip-flops are used to store the
pre-calculated CRC and other error detection circuitry option bits.
The error detection circuitry in Cyclone III device family uses a 32-bit CRC IEEE 802
standard and a 32-bit polynomial as the CRC generator. Therefore, a single 32-bit CRC
calculation is performed by the device. If a soft error does not occur, the resulting
32-bit signature value is
0x000000,
which results in a
0
on the output signal
CRC_ERROR.
If a soft error occurs in the device, the resulting signature value is non-zero and the
CRC_ERROR
output signal is
1.
You can inject a soft error by changing the 32-bit CRC storage register in the CRC
circuitry. After verifying the failure induced, you can restore the 32-bit CRC value to
the correct CRC value using the same instruction and inserting the correct value.
1
Be sure to read out the correct value before updating it with a known bad value.
Cyclone III Device Handbook
Volume 1
December 2011 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
