A CLB element contains a pair of slices, and each slice is composed of four 6-input LUTs and eight storage elements.
- SLICE(0) – slice at the bottom of the CLB and in the left column
- SLICE(1) – slice at the top of the CLB and in the right column
These two slices do not have direct connections to each other, and each slice is organized as a column. Each slice in a column has an independent carry chain.
The AMD tools designate slices with these definitions:
- An “X” followed by a number identifies the position of each slice in a pair as well as the column position of the slice. The “X” number counts slices starting from the bottom in sequence 0, 1 (the first CLB column); 2, 3 (the second CLB column); etc.
- A “Y” followed by a number identifies a row of slices. The number remains the same within a CLB, but counts up in sequence from one CLB row to the next CLB row, starting from the bottom.
The following figure shows four CLBs located in the bottom-left corner of the die.
Figure 1. Row and Column Relationship between CLBs and Slices
