| Bits | Description |
|---|---|
| 7:4 | Reserved, 0 |
| 3:0 | Board ID 0000 = ZXN Issue 2, XC6SLX16-2FTG256, 128Mbit W25Q128JV, 24bit spi, 64K*8 core size 0001 = ZXN Issue 3, XC6SLX16-2FTG256, 128Mbit W25Q128JV, 24bit spi, 64K*8 core size 0010 = ZXN Issue 4, XC7A15T-1CSG324, 256Mbit MX25L25645G, 32bit spi, 64K*34 core size |