PIC 16F1716运算放大器输出到比较器输入不起作用，规则是什么？

你好，有经验的朋友。我做了如下实验：在引脚RB1 OPA2OUT连接到C1IN -（运算放大器输出到比较器CMP1输入）。它工作- OPA2OUT产生一个波和CMP1响应，虽然MPLABYX下的代码配置器发出警告，PIN不能同时是一个输出和输入。（但是MPLAbxx是已知的）。但是尝试用OPA1OUT和C1IN对PIN RA1进行同样的操作是不起作用的。OPA1OUT产生期望的波，CMP1不起反应。（BTW，它以相同的方式工作，而不是OOFUT，我使用PIN作为数字输出和比较器输入，虽然在数据表中写道：”一般来说，当端口引脚上启用外围设备时，该引脚不能用作一般PUPO。在这两种情况下，比较器的输入+内部连接到DAC。为什么会这样？有没有什么我错过的规则，或者像这样的案例应该在做一个项目时总是检查？Regards.Kristoff。



      以下为原文

    Hello more experienced friends. I made an experiment as follow:
On pin RB1 OPA2OUT is connected to C1IN3- ( op amp output to comparator CMP1 input ). It works - OPA2OUT produces a wave and CMP1 responds, though Code Configurator under MPLAB_X sends warning that the pin cannot be an output and input at the same time. ( But MPLAB_X is known for this ).
But trying to do the same with OPA1OUT and C1IN1- on pin RA1 it doesn't work. OPA1OUT produces desired wave and CMP1 doesn't react.
( BTW, it works the same way when instead of OPAOUT I use the pins as digital outputs and comparator inputs, although in the datasheet is written " In general, when a peripheral is enabled on a port pin, that pin cannot be used as a general purpose output." )
In both cases +input of the comparator is internally  connected to DAC.
Why it is that? Is there any rule I missed or cases like this should be always checked while making a project?

Regards.
Kristoff.