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AR# 40212

Configuration FPGA Multiboot - Can I multiboot a master and slave device at the same time in a parallel or slave daisy chain?


Can I multiboot a master and slave device at the same time in a parallel or slave daisy chain?


Xilinx FPGAs do not natively support a multiboot or a fallback reconfiguration when you use a daisy chain configuration.

Fallback in a Daisy Chain

Fallback in a daisy chain cannot work because it relies on the master to control the configuration interface. Because the DONE pins are tied together in a daisy chain, this is not possible. If multiboot fallback-like functionality is needed in a daisy chain, thenexternal control logic is required to acheive this.

Multiboot in a Daisy Chain - No Fallback

For serial or parallel daisy chains with a master and a series of slaves, there is a way to make multiboot work. For chains containing slaves only, multiboot is not possible.

For a daisy chain, you must tie themaster and slave device DONE pins together. If a multiboot of the master is executed,its DONE pin will be driven low. Theslave devices, however, do not see any multiboot command and drive their DONE pins high. This prevents the slaves from seeing any configuration data, and, therefore, they remain configured with the original image, and the new multiboot image will not load.

Before themultiboot of themaster device,you must reset the slave with PROG_B or an IPROG to clear the configuration memory, and, therefore set DONE to low. The PROG_B of the slave can be connected to master's I/O or controlled by an external device. Before the multiboot, assert the PROG_B of slave to reset slave. Alternatively, some communication can be passed from the master to theslave to prompt it to perform an IPROG.After the slave has been cleared, the master can multiboot and the system will start up as if from a POR or first boot.

Errors on the master or slave during this process will result in the chain of devices in an undetermined state. Fallback will not work and a hard reset is required to recover the system.

AR# 40212
Date Created 04/08/2011
Last Updated 03/04/2013
Status Active
Type General Article
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