SystemC Data Types

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SystemC Data Types
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SystemC Data Types

• C Built-in Types
• bool
• char
• int
• float
• strings
• pointers / references

not synthesisable
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SystemC Data Types

• bit and bit vector
• sc_bit, sc_bvltNgt
• four-state logic
• sc_logic, sc_lvltNgt
• 0 Logical 0
• 1 Logical 1
• Z High Impedance
• X Unknown

• Fixed Precision ints
• 64 Bits
• sc_intltNgt
• sc_uintltNgt
• Arbitrary Precision
• Up to 512 Bits
• sc_bigintltNgt
• sc_biguintltNgt

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SystemC Data Types

• Fixed Point Types
• Useful in DSP applications
• Specify Quantization and Saturation Behavior
• sc_fixedltwl, iwl, q_mode, o_mode, n_bitsgt
• wl Total WorD Length
• iwl Integer Word Length
• q_mode Quantization Mode
• o_mode Overflow Mode
• n_bits Number of Saturated Bits

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SystemC Data Types

• Common Characteristics
• Native C types (int, float, string) and SystemC
  types may be mixed.
• Equality and bitwise operators (, ltlt, gtgt)
• All SystemC Data Types
• Arithmetic and relational operators (, -, lt, gt)
• Numeric data types only
• Overloaded assignment operators
• Provides conversion between different data types.
• Conversion may truncate data when necessary.
• e.g. myInt myFloat

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SystemC Data Types

• Utility Methods
• Bit Select get and set specific bits
• Range Select get and set a range of bits
• Concatenation join bits
• Bitwise Reduction
• Integer Conversion
• String input and output

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SystemC Data Types

• Bit Select
• Read or write to a specific bit in a variable.
• C operator overloaded to provide read/write
  access.
• e.g.

sc_intlt4gt myInt // 4-bit signed
integer myInt1 true // Set bit 1 to
true.bool myBool bool b1 myInt0.to_bool() //
Read bit 0
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SystemC Data Types

• Part Select
• Read/write a contiguous subset of bits within the
  variable.
• Available methods
• range(int, int)
• C operator()
• e.g.

sc_intlt8gt myInt 2 //
00000010 myInt.range(3, 2) myInt.range(1, 0)
// 00001010
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SystemC Data Types

• Concatenation
• Concatenate the bits of two variables together.
• Available methods
• concat(arg0, arg1)
• C comma operator operator,

sc_intlt8gt U1 2 // 00000010 sc_intlt2gt U2 1
// 01 sc_intlt8gt U3 (true, U1.range(3,0), U2,
U20) // U3
10010011 (U20, U10, U1.range(7,6))
U1.range(3, 0)
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SystemC Data Types

• Bitwise Reduction
• Performs bitwise operation on all bits in integer
  or vector.
• Returns bool.
• Operations
• and_reduce() - Bitwise AND between all bits
• nand_reduce() - Bitwise NAND between all bits
• or_reduce() - Bitwise OR between all bits
• nor_reduce() - Bitwise NOR between all bits
• xor_reduce() - Bitwise XOR between all bits
• xnor_reduce() - Bitwise XNOR between all bits

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SystemC Data Types

• Integer Conversion
• All SystemC data types
• accept C integer assignment.
• convert to C interger types
• Conversion Methods
• to_int() - Convert to native int type
• to_uint() - Convert to native unsigned type
• to_long() - Convert to native long type
• to_ulong() - Convert to native unsigned long type
• to_uint64() - Convert to native 64-bit unsigned
  integer
• to_int64() - Convert to native 64-bit signed
  integer

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SystemC Data Types

• String input and output
• All SystemC data types
• can be set by reading from a C input text
  stream
• can print their value to a C output text stream

void scan(istream input) void print(ostream
output)
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Debugging
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Text-based Debugging

• C printf debugging

printf(Hello World) cout ltlt Hello World ltlt
endl
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Text-based Debugging

• Constructor Debugging
• Find out how your design is built up when the
  simulation starts.
• Use the name() method to identify SystemC classes

SC_CTOR(nand2) cout ltlt Constructing nand2
ltlt name() ltlt endl ... ... OUTPUT Construc
ting stim Constructing nand2 exor2.N1 Constructung
nand2 exor2.N2
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Text-based Debugging

• Debugging methods available on all SystemC
  objects
• const char name()
• Returns the name of the object
• const char kind()
• Returns the objects sub-class name
• void print(ostream out)
• Prints the objects name to the output stream
• void dump(ostream out)
• Prints the objects diagnostic data to the output
  stream.

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Text-based Debugging

• Debugging threads and methods
• All SystemC data types can be printed to cout.
• e.g. print inputs A, B, and F to cout in a table

OUTPUT Time A B F 10 ns 1 0 0 20 ns
1 1 0 30 ns 1 1 1 40 ns 0 0 1
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Text-based Debugging
SC_MODULE(mon) sc_inltboolgt A,B,F
sc_inltboolgt Clk void monitor() cout
ltlt "Time A B F" ltlt endl while (true)
cout ltlt sc_time_stamp() ltlt ", "
cout ltlt A.read() ltlt ", " cout ltlt
B.read() ltlt ", " cout ltlt F.read() ltlt
endl wait() // wait for 1 clock cycle
SC_CTOR(mon)
SC_THREAD(monitor) sensitive ltlt Clk.pos()

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Advanced Debugging

• Standard C debugging tools
• GDB, etc...
• SystemC-specific debuggers and visualizers.

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Advanced Debugging
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Wave-form Debugging

• Requires adding additional SystemC statements to
  sc_main()
• Wave-form data written to file as simulation
  runs.
• Sequence of operations
• Declare and create the trace file
• Register signals or events for tracing
• Run the simulation
• Close the trace file

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Wave-form Tracing
int sc_main(int argc, char argv)
sc_signalltboolgt ASig, BSig, FSig sc_clock
TestClk("TestClock", 10, SC_NS,0.5, 1, SC_NS)
// Set up simulation ... // Set up trace
file sc_trace_file Tf Tf
sc_create_vcd_trace_file("traces") //
Create Trace File ((vcd_trace_file)Tf)-gtsc_set_
vcd_time_unit(-9) // Set time unit
sc_trace(Tf, ASig , "A" ) // Register
signals sc_trace(Tf, BSig , "B" )
// and variables. sc_trace(Tf, FSig ,
"F" ) sc_trace(Tf, DUT.S1, "S1")
sc_trace(Tf, DUT.S2, "S2") sc_trace(Tf,
DUT.S3, "S3") sc_start() // run
forever // Start the simulation
sc_close_vcd_trace_file(Tf) // Close the trace
file return 0
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Wave-form Tracing

• Sample Output

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Questions?
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References

• http//embedded.eecs.berkeley.edu/Respep/Research/
  hsc/abstract.htmlmotivation
• http//www.esperan.com/pdf/Esperan_SystemC_tutoria
  l.pdf
• http//www.doulos.com/knowhow/systemc/tutorial/
• http//www.comelec.enst.fr/hdl/sc_docs/systemc_qui
  ckreference.pdf
• http//www.ecsi-association.org/ecsi/projects/odet
  te/files/6.systemc.pdf