 | Services - tools - models - for embedded software development |
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| Services - tools - models - for embedded software development |
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The functionality of this class is identical to that of its Verilog
counterpart. On each positive clock edge, the freeze signal for the
write back pipeline stage in the CPU control unit is checked. If the
value is clear, the current instruction being executed is read. If
the instruction is a special l.nop instruction,
the appropriate behavior is implemented.
The class has a single port, clk of type
sc_in<bool>, which is connected to the
system clock.
Access to signals within the Verilator ORPSoC model is
provided by the OrpsocAccess class, an
instance of which is passed to the constructor.
The implementation of OrpsocAccess is
covered in the chapter on Verilator modeling Chapter 6. It provides a number of methods to
access signals in the model. Those of particular interest here
are:
getWbFreeze
Gives the bool value of the CPU control unit
write back freeze signal, wb_freeze.
getWbInsn
Gives the uint32_t value of the CPU control
unit write back instruction, wb_insn.
getGpr (regNum)
Get the value of the ORPSoC GPR
regNum from the CPU register file in
rf_a.
The constructor declares a SystemC method,
checkInstruction, which will check for
a l.nop instruction on the positive edge of
each clock.
This function is called on the positive edge of each clock
cycle. It uses the accessor class getWbFreeze
and getWbInsn functions to check for special
l.nop instructions. It implements behavior as
follows:
l.nop 1
Gets the value in GPR 3 using the accessor
getGpr function, which is the return
code from the function. Prints out a time stamp (using the
SystemC function, sc_time_stamp)
followed by a message that the simulation is exiting with
the return code obtained. Then calls the SystemC function,
sc_stop to terminate model execution.
l.nop 2
Gets the value in GPR 3 using the accessor
getGpr function. Prints out a time
stamp (using the SystemC function,
sc_time_stamp) followed by a message
reporting the value found in GPR 3.
l.nop 3
This is the printf function, but is not
implemented. Prints out a time stamp (using the
SystemC function, sc_time_stamp)
followed by the text "printf".
l.nop 4
Gets the value in GPR 3 using the accessor
getGpr function, the bottom 8 bits of
which are the character to print. Prints the character to
standard output, and then flushes it. This avoids any issues
with C++ library buffering if redirecting the output during
a slow run.
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5.1.1.
Vorpsoc_fpga_top
|  | 5.1.3.
ResetSC
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