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Arbitrary Width Bit Type
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sc_bit is one bit wide, SystemC provides sc_bv or SystemC Bit Vector for multi bit vector declaration. The width of the vector is specified in integer . The rightmost index of the vector is 0 and is also the least significant bit. A width of M sets the vector size and direction to be M-1 down to 0 with the Mth bit being the most significant bit. |
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If assignement to bit vector variable is less size (width), then rest of the bits are extened with 0. If they are more, then they are truncated. |
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The sc_bv type introduces some new operators and methods that perform bit reduction, range selection. Bit reductions and range selection can not be performed on port and signals. |
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Operator
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Description
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Usage
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&
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Bitwise AND
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expr1 & expr2
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Bitwise OR
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expr1 | expr2
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^
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Bitwise XOR
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expr1 ^ expr2
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~
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Bitwise NOT
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~expr
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&=
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AND assignment
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variable &= expr
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|=
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OR assignment
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variable |= expr
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^=
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XOR assignment
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variable ^= expr
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=
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Equality
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expr1 = expr2
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!=
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Inequality
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expr1 != expr2
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[]
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Bit selection
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variable [index]
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(,)
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Concatenation
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(expr1, expr2, expr3)
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Methods in Arbitrary Width Bit Type |
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Methods
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Description
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Usage
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range()
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Range selection
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variable.range(indexl, index2)
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and_reduce()
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Reduction AND
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variable.and_reduce()
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or_reduce()
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Reduction OR
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variable.or_reduce()
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xor_reduce()
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Reduction XOR
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variable.xor_reduce()
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Example : Arbitrary Width Bit Type
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1 #include <systemc.h>
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3 int sc_main (int argc, char* argv[]) {
4 sc_bv<8> data_bus ;
5 sc_bv<16> addr_bus ;
6 sc_bit parity ;
7 // Assign value to sc_bv
8 data_bus = "00001011";
9 cout <<"Value of data_bus : " << data_bus << endl;
10 // Use range operator
11 addr_bus.range(7,0) = data_bus;
12 cout <<"Value of addr_bus : " << addr_bus << endl;
13 // Assign reverse to addr bus using range operator
14 addr_bus.range(0,7) = data_bus;
15 cout <<"Value of addr_bus : " << addr_bus << endl;
16 // Use bit select to set the value
17 addr_bus[10] = "1";
18 cout <<"Value of addr_bus : " << addr_bus << endl;
19 // Use reduction operator
20 parity = data_bus.xor_reduce();
21 cout <<"Value of parity : " << parity << endl;
22
23 return 1;
24 }
You could download file arb_width_bit_type.cpp here
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Simulation : Arbitrary Width Bit Type
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SystemC 2.0.1 --- Oct 6 2006 19:17:37
Copyright (c) 1996-2002 by all Contributors
ALL RIGHTS RESERVED
Value of data_bus : 00001011
Value of addr_bus : 0000000000001011
Value of addr_bus : 0000000011010000
Value of addr_bus : 0000010011010000
Value of parity : 1
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Arbitrary Width Logic Type
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sc_logic is one bit wide, SystemC provides sc_lv or SystemC Bit Vector for multi logic vector declaration. The width of the vector is specified in integer . The rightmost index of the vector is 0 and is also the least significant bit. A width of M sets the vector size and direction to be M-1 down to 0 with the Mth bit being the most significant bit. |
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If assignement to logic vector variable is less size (width), then rest of the bits are extened with 0. If they are more, then they are truncated. |
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The sc_lv type introduces some new operators and methods that perform bit reduction, range selection. Bit reductions and range selection can not be performed on port and signals. |
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No arthemetic operations are allowed on sc_lv types, instead they need to be performed on sc_int or sc_uint and then assigned to sc_lv. |
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Example : Arbitrary Width Logic Type
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1 #include <systemc.h>
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3 int sc_main (int argc, char* argv[]) {
4 sc_lv<8> data_bus (sc_logic ('z')); // All bits are Z
5 sc_lv<16> addr_bus ; // All bits are X
6 sc_logic parity ;
7 // Print Default value of data_bus
8 cout <<"Value of data_bus : " << data_bus << endl;
9 // Assign value to sc_bv
10 data_bus = "00001011";
11 cout <<"Value of data_bus : " << data_bus << endl;
12 // Use range operator
13 addr_bus.range(7,0) = data_bus;
14 cout <<"Value of addr_bus : " << addr_bus << endl;
15 // Assign reverse to addr bus using range operator
16 addr_bus.range(0,7) = data_bus;
17 cout <<"Value of addr_bus : " << addr_bus << endl;
18 // Use bit select to set the value
19 addr_bus[10] = "1";
20 cout <<"Value of addr_bus : " << addr_bus << endl;
21 // Use reduction operator
22 parity = data_bus.xor_reduce();
23 cout <<"Value of parity : " << parity << endl;
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25 return 1;
26 }
You could download file arb_width_logic_type.cpp here
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Simulation : Arbitrary Width Logic Type
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SystemC 2.0.1 --- Oct 6 2006 19:17:37
Copyright (c) 1996-2002 by all Contributors
ALL RIGHTS RESERVED
Value of data_bus : ZZZZZZZZ
Value of data_bus : 00001011
Value of addr_bus : XXXXXXXX00001011
Value of addr_bus : XXXXXXXX11010000
Value of addr_bus : XXXXX1XX11010000
Value of parity : 1
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