Method of controlling access to storage means in numerical-control system, and numerical-control system

A numerical-control system having first storage means and second storage means having an access time longer than that of the first storage means, wherein numerical-control instructions in blocks of a numerical-control program stored in the first storage means are sequentially executed, i.e. converted into control signals, block by block,

• said numerical-control system comprising:
• instruction type storage means for previously storing the numerical-control instructions in the blocks of said numerical-control program, said numerical-control instructions being classified into waitable instructions which allow a wait between execution thereof and execution of a numerical-control instruction in a subsequent block, and unwaitable instructions which disallow a wait between execution thereof and execution of a numerical-control instruction in a subsequent block;
• and
• access control means for judging, when there is a request for access to said second storage means during execution of said numerical-control program, whether or not a numerical-control instruction in an execution block, which is a block to be executed subsequently, is a waitable instruction, and, if the numerical-control instruction is a waitable instruction, executing access to said second storage means after the numerical-control instruction in the execution block has been executed, and for executing, if the numerical-control instruction in the execution block is an unwaitable instruction, processing of a subsequent block after the numerical-control instruction in the execution block has been executed without executing access to said second storage means.