User guide

Spartan-6 FPGA Configuration User Guide www.xilinx.com 131
UG380 (v2.7) October 29, 2014
Chapter 7
Reconfiguration and MultiBoot
MultiBoot Overview
Because Spartan®-6 FPGAs are reprogrammable in the system, some applications reload
the FPGA with one or more bitstream images during normal operation. In this way, a
single smaller FPGA, reprogrammed multiple times, replaces a much larger and more
expensive ASIC or FPGA programmed just once.
A variety of methods can be used to reprogram the FPGA during normal operation. The
downloaded configuration modes inherently provide this capability. Via an external
“intelligent agent,” such as a processor, microcontroller, computer, or tester, an FPGA can
be reprogrammed numerous times. The downloaded modes are available on all
Spartan-6 FPGA families.
Spartan-6 FPGAs include a capability called MultiBoot that allows the FPGA to selectively
reprogram and reload its bitstream from an attached external memory. The MultiBoot
feature allows the FPGA application to load two or more FPGA bitstreams under the
control of the FPGA application. The FPGA application triggers a MultiBoot operation,
causing the FPGA to reconfigure from a different configuration bitstream. After a
MultiBoot operation is triggered, the FPGA restarts its configuration process as usual. The
INIT_B pin pulses Low while the FPGA clears its configuration memory, and the DONE
output remains Low until the MultiBoot operation successfully completes.
MultiBoot is supported in SPI x1, x2, x4, and BPI configuration modes.