圖2-9為SIEMENS 840D系統軟件構成框圖。圖中一些英文符號解釋如下:
SRAM??? (Staic Storgl RAW:靜態儲存器;
DPR???? (Dual-Port RAM):雙口RAM;
DRAM??? (Dynamic Storge RAM):動態儲存器;
MPI???? (Multi-Port-Interface ):多通信接口;
MMC???? (Man Machine Communction):人機界面;
NCU???? (Numerical Control Unit):數字控制單元:
NCK???? (Numerical Control Kernel):數字控制核;
PCMCIA? (Personal Computer Memory Card International Association):個人計算機儲存卡協。