From 53d4a0be53776cb2cbc83d9bd245935594eb37f4 Mon Sep 17 00:00:00 2001
From: Clifford Wolf
-The checkerboard pattern in the picture visualizes which bits are assoziated +The checkerboard pattern in the picture visualizes which bits are associated with which tile. The height of the configuration block is 16 for all tile types, but the width is different for each tile type. IO tiles have configurations that are 18 bits wide, LOGIC tiles are 54 bits wide, and @@ -126,12 +126,12 @@ RAM tiles are 42 bits wide. (Notice the two slightly smaller columns for the RAM
The IO tiles on the top and bottom of the chip use a strange permutation pattern for their bits. It can be seen in the picture that their columns are spread out horizontally. What cannot be seen in the picture is the columns also are not in order and the bit -positions are vertically permutated as well. The CramIndexConverter class in icepack.cc encapsulates the calculations +positions are vertically permuted as well. The CramIndexConverter class in icepack.cc encapsulates the calculations that are neccessary to convert between tile-relative bit addresses and CRAM bank-relative bit addresses.
-The black pixels in the image correspond to CRAM bits that are not assoziated with any IO, LOGIC or RAM tile. +The black pixels in the image correspond to CRAM bits that are not associated with any IO, LOGIC or RAM tile. Some of them are unused, others are used by hard IPs or other global resources. The iceunpack tool reports such bits, when set, with the ".extra_bit bank x y" statement in the ASCII output format.
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