SystemC time

The first thing to distinguish is SystemC Simulation time and Machine execution time , Machine execution time It is our CPU The physical time spent by the physical machine running the program , This time is the time we really feel ,1s,1min … ; and SystemC The simulation time is SystemC Program execution kernel Scheduled time ,SystemC Simulation time does not correspond to physical execution time in any granularity , Like a program , stay SystemC Simulation time from 0ns To 100 ns It took CPU The physical time is 10s; It is not possible to deduce from 100ns To 200ns The process also costs 10s The physical time of .

about 1G Hz Of silicon ( Hardware chip ),1s Is to execute 1G individual cycle; But if it's running RTL code Of Simulation, Then run 1 m Cycle It will probably cost CPU Physical time 1h, because Simulation It's serial execution . because Simulation Running too slowly , So we usually use emulation platform To run RTL code, use FPGA Hardware devices to speed up the simulation process .

SystemC It uses pure software to simulate the implementation of hardware , The simulation speed of the program is closely related to our code implementation . It can be used in general cycle per S To express the simulation speed , That is, the physical execution time 1S,SystemC How many times has the simulation time been advanced cycle, If we SystemC The program is configured with 1G Hz, be 1 individual cycle Namely 1ns.

You can use... In the code sc_core::sc_time_stamp() Get the current simulation time .

SC_ZERO_TIME yes SystemC Define a time macro , Express delta T, yes SystemC Kernel The smallest unit of time for scheduling , For programmers , In most cases, it can be simply understood as 0T. notes ： If it involves SystemC Problems caused by scheduling sequence , You may need to consider delta T Influence .

Class sc_time yes SystemC Type of time used ,SystemC Supported time units enum sc_time_unit {SC_FS = 0, SC_PS, SC_NS, SC_US, SC_MS, SC_SEC};

Simulation time is an integer quantity. Simulation time is initialized to zero at the start of simulation and increases monotonically during simulation. The physical significance of the integer value representing time within the kernel is determined by the simulation time resolution. Simulation time and time intervals are represented by class sc_time. Certain functions allow time to be expressed as a value pair having the signature <double,sc_time_unit>

The simulation time is an integer . The simulation time is initialized to zero at the beginning of the simulation , Monotonically increase in the simulation process . The physical meaning of the integer value representing the time in the core is determined by the resolution of the simulation time . The simulation time and time interval are determined by the class sc_time Express . Some functions allow you to time Expressed as < double sc_time_unit> Value .