Fence for SSI Technology Devices - Fence for SSI Technology Devices - 2.3 English - XAPP1335

Isolation Design Flow for Zynq UltraScale+ MPSoCs and UltraScale+ FPGAs (XAPP1335)

Document_ID
XAPP1335
Release_Date
2026-08-04
Revision
2.3 English

In the case of SSI technology devices, the SLR boundaries serve as natural isolation boundary/fence. No additional fence is required between SLRs if an SLR region contains only one isolated Pblock. If every SLR region consists of a single isolated Pblock, no additional fence is needed. However, if an SLR region contains multiple isolated Pblocks, the appropriate fence is needed between them

The following figure shows four isolated Pblocks, highlighted in four different colors, drawn in each SLR regions of an self-sovereign identities technology (SSI technology) device. No explicit fence is needed between the Pblocks as the SLR boundaries serve as isolation fence.

Note: This is applicable only when there is no communication between the four isolated regions, including clocks. If communication is needed between the isolated regions, refer to SSIT Fence with Communication Between Isolated Modules.
Figure 1. Vivado IDE Screen Capture of an IDF Design Implemented on an SSI Technology Device

In the following figure, no fence is needed between Isolated Pblock 1 and Isolated Pblock 2 because they have the SLR boundary of region 2 and 1 as a natural isolation fence. But a fence is still required between Isolated Pblock 3 and Isolated Pblock 1, and between Isolated Pblock 3 and Isolated Pblock 2. Be aware that the light-grey color in the diagram is the FPGA logic. A fence is required between the bottom right corner of Isolated Pblock 1, and the top left corner of the second half of Isolated Pblock 3, to account for diagonal adjacency violation.

Figure 2. Isolated Design with Three Modules on an SSI Technology Device