Package: prim_util_pkg

Copyright lowRISC contributors.
Licensed under the Apache License, Version 2.0, see LICENSE for details.
SPDX-License-Identifier: Apache-2.0
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Description
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• Math function: Number of bits needed to address |value| items.
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• 0 for value == 0
• vbits = 1 for value == 1
• ceil(log2(value)) for value > 1
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• The primary use case for this function is the definition of registers/arrays
• which are wide enough to contain |value| items.
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• This function identical to $clog2() for all input values except the value 1;
• it could be considered an "enhanced" $clog2() function.
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• Example 1:
• parameter Items = 1;
• localparam ItemsWidth = vbits(Items); // 1
• logic [ItemsWidth-1:0] item_register; // items_register is now [0:0]
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• Example 2:
• parameter Items = 64;
• localparam ItemsWidth = vbits(Items); // 6
• logic [ItemsWidth-1:0] item_register; // items_register is now [5:0]
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• Note: If you want to store the number "value" inside a register, you need
• a register with size vbits(value + 1), since you also need to store
• the number 0.
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• Example 3:
• logic [vbits(64)-1:0] store_64_logic_values; // width is [5:0]
• logic [vbits(64 + 1)-1:0] store_number_64; // width is [6:0]
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