uvm_reg_field——寄存器模型（二）

　　uvm_reg_field是最基本寄存器单元。

typedef class uvm_reg_cbs;

//-----------------------------------------------------------------
// CLASS: uvm_reg_field
// Field abstraction class
//
// A field represents a set of bits that behave consistently
// as a single entity.
//
// A field is contained within a single register, but may
// have different access policies depending on the address map
// use the access the register (thus the field).
//-----------------------------------------------------------------
class uvm_reg_field extends uvm_object;