问题的提出

用KEIL进行软件仿真，想观察一下处理器STM32F091RCY的I2C和DAC引脚输出的波形，发现无法向波形中添加信号，如下图所示

当在命令行中输入 dir vtreg 指令时，仅仅能够显示内核的寄存器，外设的寄存器无法输出：

dir vtreg
    CURR_TID:  ulong, value = 0x00000000
       TRAPS:  ulong, value = 0x00000000
     TRIGFLT:  ulong, value = 0x00000000
       STCLK:  ulong, value = 0x00000000
        XTAL:  ulong, value = 0x007A1200
       CLOCK:  ulong, value = 0x007A1200

网上寻找答案，发现所有的关于软件逻辑分析仪的示例都是用器件STM32F103

问题的答案

KEIL5仅对某些器件的外设支持仿真，KEIL官方给出了网站
，在该网页中，列出了支持软件仿真的器件，如：

1. 对于STMicroexectronics公司的处理器，仅支持STM32F101和STM32F103.
2. 对于NXP公司的处理器，仅支持LPC1111, LPC1112, LPC1113, LPC1114四个系列.

这也难怪，网上给出的KEIL的软件逻辑分析仪的仿真示例都是用STM32F103这个器件。

问题的解决

为了仿真I2C的程序段，在STM32CUBE MX中，将器件改为STM32F103C8，重新进行仿真，在Option for Target中的Debug中，按下图进行设置：

进入debug界面，在命令行中输入DIR VTREG, 显示出外设的寄存器：

DIR VTREG
    CURR_TID:  ulong, value = 0x00000000
       TRAPS:  ulong, value = 0x00000000
     TRIGFLT:  ulong, value = 0x00000000
       STCLK:  ulong, value = 0x000F4240
         OSC:  ulong, value = 0x007A1200
      SYSCLK:  ulong, value = 0x007A1200
      HSI_RC:  ulong, value = 0x007A1200
       OSC32:  ulong, value = 0x00008000
      LSI_RC:  ulong, value = 0x00008000
        HCLK:  ulong, value = 0x007A1200
       PCLK1:  ulong, value = 0x007A1200
       PCLK2:  ulong, value = 0x007A1200
      RTCCLK:  ulong, value = 0x00008000
     IWDGCLK:  ulong, value = 0x00008000
      USBCLK:  ulong, value = 0x007A1200
      ADCCLK:  ulong, value = 0x003D0900
     TIMXCLK:  ulong, value = 0x007A1200
     TIM1CLK:  ulong, value = 0x007A1200
        BOOT:  uchar, value = 0x00
       PORTA: ushort, value = 0x0000
       PORTB: ushort, value = 0x0000
       PORTC: ushort, value = 0x0000
       PORTD: ushort, value = 0x0000
        S1IN: ushort, value = 0xFFFF
       S1OUT: ushort, value = 0x0000
      S1TIME:  uchar, value = 0x01
        S2IN: ushort, value = 0xFFFF
       S2OUT: ushort, value = 0x0000
      S2TIME:  uchar, value = 0x01
        S3IN: ushort, value = 0xFFFF
       S3OUT: ushort, value = 0x0000
      S3TIME:  uchar, value = 0x01
     SPI1_IN: ushort, value = 0x0000
    SPI1_OUT: ushort, value = 0x0000
     SPI2_IN: ushort, value = 0x0000
    SPI2_OUT: ushort, value = 0x0000
     I2C1_IN: ushort, value = 0xFFFF
    I2C1_OUT: ushort, value = 0xFFFF
     I2C2_IN: ushort, value = 0xFFFF
    I2C2_OUT: ushort, value = 0xFFFF
      CAN1ID:  ulong, value = 0x00000000
       CAN1L:  uchar, value = 0x00
      CAN1B0:  uchar, value = 0x00
      CAN1B1:  uchar, value = 0x00
      CAN1B2:  uchar, value = 0x00
      CAN1B3:  uchar, value = 0x00
      CAN1B4:  uchar, value = 0x00
      CAN1B5:  uchar, value = 0x00
      CAN1B6:  uchar, value = 0x00
      CAN1B7:  uchar, value = 0x00
      CAN1IN: ushort, value = 0x0000
     CAN1OUT: ushort, value = 0x0000
    ADC1_IN0:  float, value = 0
    ADC1_IN1:  float, value = 0
    ADC1_IN2:  float, value = 0
    ADC1_IN3:  float, value = 0
    ADC1_IN4:  float, value = 0
    ADC1_IN5:  float, value = 0
    ADC1_IN6:  float, value = 0
    ADC1_IN7:  float, value = 0
    ADC1_IN8:  float, value = 0
    ADC1_IN9:  float, value = 0
   ADC1_IN10:  float, value = 0
   ADC1_IN11:  float, value = 0
   ADC1_IN12:  float, value = 0
   ADC1_IN13:  float, value = 0
   ADC1_IN14:  float, value = 0
   ADC1_IN15:  float, value = 0
      VTEMP1:  float, value = 3.29999995
     VREFINT:  float, value = 3.29999995
       VREFP:  float, value = 3.29999995
       VREFN:  float, value = 0
    ADC2_IN0:  float, value = 0
    ADC2_IN1:  float, value = 0
    ADC2_IN2:  float, value = 0
    ADC2_IN3:  float, value = 0
    ADC2_IN4:  float, value = 0
    ADC2_IN5:  float, value = 0
    ADC2_IN6:  float, value = 0
    ADC2_IN7:  float, value = 0
    ADC2_IN8:  float, value = 0
    ADC2_IN9:  float, value = 0
   ADC2_IN10:  float, value = 0
   ADC2_IN11:  float, value = 0
   ADC2_IN12:  float, value = 0
   ADC2_IN13:  float, value = 0
   ADC2_IN14:  float, value = 0
   ADC2_IN15:  float, value = 0
      VTEMP2:  float, value = 3.29999995

同时，也可以向软件逻辑分析仪中添加信号了。