X寄存器是否可用于写入TIMx_CCRyH/L寄存器？

我正在研究PWM输出的用法。我找到了一个代码，用于在FWLib源代码stm8s_tim3.c的TIM3_OC2Init函数中写入TIM3_CCR2H / L寄存器。源代码对定时器寄存器执行两次8位写操作，如下所示。
 
 
 / *设置脉冲值* /
 TIM3-> CCR2H =（u8）（TIM3_Pulse> 8）;
 TIM3-> CCR2L =（u8）（TIM3_Pulse）;
 
我认为当写操作被描述为一个16位写操作时，程序会更简单，如下所示。
 
 volatile u16 TIM3_CCR2 @ 0x00532F;
 ：
 TIM3_CCR2 =（u16）TIM3_Pulse;
 
但是使用16位变量写入定时器寄存器的程序已经失败，但是该行肯定被编译成源自X寄存器的LDW指令。
 
为什么这个程序失败了？ LDW指令的WRITE操作顺序是否与定时器寄存器的预期不同？
 
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[此消息由：st16于10-01-2010 15:34编辑]



以下为原文




I am investigating the usage of the PWM output. I found a code to write the TIM3_CCR2H/L registers at the TIM3_OC2Init function of the FWLib source code stm8s_tim3.c The source code behaves two 8-bit write operations for the timer registers as follows.



/* Set the Pulse value */  
TIM3->CCR2H = (u8)(TIM3_Pulse >> 8);  
TIM3->CCR2L = (u8)(TIM3_Pulse);  

I assumed that the program would be more simple when the write operation is described as one 16-bit write operation like following.  


volatile u16 TIM3_CCR2 @ 0x00532F;  
:  
TIM3_CCR2 = (u16)TIM3_Pulse;  

But the program using a 16-bit variable to write the timer register has been failed, however the the line is certainly compiled into an LDW instruction sourced from X register.  

Why this program has been failed ? Is the WRITE operation order of the LDW instruction different from what the timer register expected ?  

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[ This message was edited by: st16 on 10-01-2010 15:34 ]

嗨，
 
 
我认为这是一种安全机制，它首先在CCR1H之前写入CCR2H寄存器。
 
问候
阿尼斯



以下为原文




Hi,


I think that is a security mechanism that is consist to write first the CCR2H register before the CCR1H.  

Regards  
Anis

嗨，阿尼斯，
 
 
你是对的，参见参考手册pag。 161第17.5.1段（适用于TIM1，但对其他计时器也有效）。在8位微控制器上，这种读写机制保护通常用于16位或10位寄存器的r / w访问，如ADC转换值的情况。
 
布拉佐夫

嗨，阿尼斯，布拉佐夫
 
 
我假设该机制是出于安全原因而许多其他具有16位定时器的8位MCU具有相同类型的机制。 STM7是合理的，因为STM7只有8位寄存器。
 
但是STM8有16位寄存器X和Y.我想知道为什么固件库仍然使用对16位定时器寄存器的8位访问，以及为什么STM8在16位X访问16位寄存器时会失败寄存器。
 
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noritan.org



以下为原文




Hi Anis, brazov


I assumes that the mechanism is for security reason and many other 8-bit MCU with 16-bit timer have same kind of one. It is reasonable for STM7 because STM7 has 8-bit registers only.  

But STM8 has 16-bit registers X and Y. I wonder why the firmware library is still using 8-bit access to the 16-bit timer registers and why STM8 will fail if access to the 16-bit register by the 16-bit X register.  

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