针对SDRAM控制器的自动刷新指令控制方法，提出了一种周期分散刷新算法。首先，使用Verilog HDL编写SDRAM控制器。在读写过程，根据SDRAM时钟频率和存储阵列行数，确定连续读/写的次数m/n。连续m/n次读/写操作后，控制器发出一次自动刷新指令。在非读写过程，根据状态机长期处于空闲状态的特点，控制器定时发出自动刷新请求，从而周期地发出自动刷新指令。然后，基于光电测量系统对算法进行验证。实验结果表明控制器周期、及时、准确地发出了自动刷新指令，读写指令执行效率提高了0.39%。该算法解决了自动刷新指令滞后的问题，提高了读写指令执行效率，具有良好的移植性。

Aiming at the control method of Auto_Refresh instruction in SDRAM controller, a periodic and distributed refresh algorithm is proposed. First, A SDRAM controller is compiled by Verilog HDL. In reading or writing process, m, n, the continuous times of reading or writing is confirmed by SDRAM clock frequency and the row number of L-BANK. An Auto_Refresh instruction is given after m reading or n writing instructions. Because FSM is almost always in the state of IDLE in the process after reading and writing, Auto_Refresh instruction is given periodically. Then, the Photoelectric Measurement System is used for experimental verification. The experimental results show that SDRAM controller can give Auto_Refresh periodically, timely and accurately, and the execution efficiency of reading and writing instructions is improved by 0.39%. This algorithm solves the problem of Auto_Refresh instruction lagged behind, improves the execution efficiency of reading and writing instructions, and has good portability.