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代码说明：

  假设每个从设备中有可访问APB寄存器16个，位宽均为32比特，16个寄存器的访问地址计算方式为 基址 +　寄存器编号左移２位（byte 偏移）(Assuming that there are 16 accessible APB registers in each slave device, the bit width is 32 bits, and the access address of 16 registers is calculated by base address + register number left shift 2 bits (byte offset).)