第三部分 PLI 程序

PLI提供两种类型的程序：Access程序；任务和函数程序。Access 程序是能访问verilog内部的信息的C编程语言……

PLI提供两种类型的程序，他们是

• access程序
• 任务和函数程序

PLI2.0把access程序和tf程序整合为VPI函数，也澄清了PLI中的一些confusion。

Access 程序
Access 程序是能访问verilog内部的信息的C编程语言。access程序能执行两个操作：

读取操作： 直接从内部数据结构中读取特定对象的数据。access程序可以读取以下对象的信息：

•   例化模块
•   模块端口
•   模块通路
•   内部模块通路 
•   顶层模块
•   例化primitive
•   Primitive terminals
•   线网
•   寄存器
•   参数
•   时序检查
•   named events
•   整型，实数和时间变量

写操作：向内部数据结构写入有关对象的新信息。

•   模块内部通路
•   模块通路
•   例化primitives
•   时序检验
•   寄存器逻辑值
•   sequential UDP逻辑值

根据access的操作，可以分为六类：

•    Fetch: 返回设计层次中不同对象信息
•    Handle: 返回设计层次中的句柄
•    Modify: 修改设计层次中各种对象的值
•    Next:   当在循环结构时，next程序寻找每个符合给定类型的对象
•    Utility: 执行许多操作，比如初始化和配置access程序环境
•    VCL：　VCL允许PLI 应用程序监测选定对象的值的改变

Access 函数参考

Routine Description acc_handle_scope() This function returns the handle to the scope of an object. The scope can be either a module, task, function, named parallel block, or named sequential block. acc_handle_by_name() This routine returns the handle to a Verilog-HDL object based on the specified name and scope. acc_handle_parent() This function returns handle for the parent primitive instance or module instance of an object acc_handle_port() This function returns handle for a module port acc_handle_hiconn() This function returns the hierarchically higher net connection to a scalar module port or a bit of a vector port acc_handle_loconn() This function returns the hierarchically lower net connection to a scalar module port or a bit of a vector port. acc_handle_path() This function returns a handle to an inter-module path that represents the connection from an output port to an input port acc_handle_modpath() This function returns handle to the path of a module acc_handle_datapath() This function returns a handle to a datapath for a module instance for the specified edge-sensitive module path acc_handle_pathin() This function returns handle for the first net connected to a module path source acc_handle_pathout() This function returns handle for the first net connected to a module path destination acc_handle_condition() This function returns a handle to the conditional expression for the specified path acc_handle_tchk() This function returns handle for the specified timing check of a module (or cell) acc_handle_tchkarg1() This function returns handle for the net connected to the first argument of a timing check acc_handle_tchkarg2() This function returns handle for the net connected to the second argument of a timing check acc_handle_simulated_net() This function returns the simulated net associated with the collapsed net passed as an argument acc_handle_terminal() This function returns handle for a primitive_terminal acc_handle_conn() This function returns handle to the net connected to a primitive terminal acc_handle_tfarg() This function returns handle for the specified argument of the system task or function associated (through the PLI mechanism) with your C-language routine` acc_fetch_attribute() This function returns the value of a parameter or specparam named as an attribute in your source description acc_fetch_paramtype() This function returns the data type of a parameter as one of three predefined integer constants. acc_fetch_paramval() This function returns the value of a parameter or specparam acc_fetch_defname() This function returns a pointer to the defining name of a module instance or primitive instance acc_fetch_fullname() This function returns a pointer to the full hierarchical name of any named object or module path acc_fetch_name() This function returns a pointer to the instance name of any named object or module path acc_fetch_delays() This function fetches different delay values for different objects acc_fetch_size() This function returns the bit size of a net, register, or port. acc_fetch_range() This function retrieves the most significant bit and least significant bit range values for a vector. acc_fetch_tfarg() This function returns value of the specified argument of the system task or function associated (through the PLI mechanism) with your C-language routine acc_fetch_direction() This function returns the direction of a port or terminal as one of three predefined integer constants. acc_fetch_index() This function returns a zero-based integer index for a port or terminal acc_fetch_edge() This function returns the edge specifier (type) of a path input or output terminal as one of these predefined integer constants. acc_set_value() This function returns a pointer to a character string indicating the logic or strength value of a net, register or variable. acc_initialize() This function initializes the environment for access routines acc_close() This function frees internal memory used by access routines; resets all configuration parameters to default values acc_configure() This function sets parameters that control the operation of various access routines acc_product_version() This function returns a pointer to a character string that indicates what version of a Verilog simulator is linked to the access routines acc_version() This function returns a pointer to a character string that indicates version number of your access routine software acc_count() This function returns an integer count of the number of objects related to a particular reference object acc_collect() This function returns a pointer to an array that contains handles for all objects related to a particular reference object acc_free() This function frees memory allocated by acc_collect acc_compare_handles() This function returns true if the two input handles refer to the same object acc_object_in_typelist() This function determines whether an object fits a type or fulltype or exhibits a property specified in an input array acc_object_of_type() This function determines whether an object fits a specified type or fulltype, or exhibits a specified property acc_next_cell() This function returns the next cell instance within the region that includes the entire hierarchy below a module acc_next_child() This function returns the next child of a module acc_next_modpath() This function returns the next path of a module acc_next_net() This function returns the next net of a module acc_next_parameter() This function returns the next parameter within a module acc_next_port() This function returns the next input, output or inout port of a module in the order specified by the port list acc_next_portout() This function returns the next output or inout port of a module in the order specified by the port list acc_next_primitive() This function returns the next gate, switch or user-defined primitive (UDP) within a module acc_next_specparam() This function returns the next specparam within a module acc_next_tchk() This function returns the next timing check within a module acc_next_terminal() This function returns the next terminal of a gate, switch or user-defined primitive (UDP) acc_next() This function within a scope, returns the next object of each type specified in object_type_array acc_next_topmod() This function returns the next top-level module acc_next_cell_load() This function returns the next load on a net inside a cell acc_next_load() This function returns the next primitive terminal driven by a net acc_next_driver() This function returns the next primitive terminal that drives a net acc_next_hiconn() This function returns the next hierarchically higher net connection to a port of a module acc_next_loconn() This function returns the next hierarchically lower net connection to a port of a module acc_next_bit() This function returns the handles of each bit in an expanded vector port or expanded vector net acc_next_input() This function returns a handle to the next input path terminal of the specified module path or datapath acc_next_output() This function returns a handle to the next output path terminal of the specified module path or datapath

使用access程序流程
就像在前面例子里看见的一样，在我们写用户应用程序的之前，要执行一系列步骤，如下：

1	#include <acc_user.h>
2
3	void pli_func() {
4		acc_initialize();
5		// Main body: Insert the user application code here
6		acc_close();
7	}

• acc_user.h: 所有有关access程序的数据结构
• acc_initialize(): 初始化变量和建立环境
• 主体： 用户定义应用
• acc-close()： 取消acc-initialize执行的操作

对象的句柄
句柄是预定义的数据类型，类似于C中的指针，用来指向设计数据库中的对象和指向任何类型的对象。句柄是access程序的支柱，PLI1.0中引入的最重要的新概念。

申明：

• handle my_handle;
• handle clock;
• handle reset;

VCL（Value change link）
VCL是一个PLI应用程序来监测被选定对象值的改变

•    事件
•    标量和矢量寄存器
•    标量线网
•    扩展的矢量线网的位选
•    未扩展的矢量线网

VCL不能提取有关下面对象的信息：

•    Bit-selects of unexpanded vector nets or registers
•    部分选择
•    存储器
•    表达式