用ICSP编程时，PIC24FJ256GB206端口B上的引脚状态是什么

一位同事发现了一个奇怪的事情发生在一个新设计的板上，当他通过MPLAB-X通过ICSP编程闪存：板是通过自己的电源供电，当他通过ICPIT3启动ICSP编程时，车载高压电源转换器突然开始运行。现在，这个转换器在引脚RB10上有一个使能线（PIC引脚23），它也是模拟引脚AN10，并且这条线主动驱动光耦合器。即，光耦合器的LED与它的阴极连接到地上，并用它的阳极连接到PIC。光耦合器隔离输出驱动MOSFET的栅极，该栅极被一个39 K电阻拉低至-12V。这意味着为了激活高压转换器，PIC输出必须DRIV。E电流通过LED从引脚上的高电压水平。我们对此感到困惑，因为我们理解PIC出来的复位与端口B引脚配置为模拟输入，直到运行代码已设置寄存器为数字。但是输入不能驱动光耦的LED，对吗？那么在通过ICSP系统编程闪存时有什么奇怪的事情发生吗？我们已经将ICSP连接到以下引脚：ICSP引脚1：MCLR（PIC引脚7）ICSP引脚4：PGED1（PIC引脚16）ICSP引脚5：PGEC1（PIC引脚15），PIC上没有这些引脚的替代用途。因此，在通过ICSP编程时有什么特别的事情可以解释这种行为吗？我附上故障信号的电路图的一个切口。



      以下为原文

    A colleague found a weird thing happening on a newly designed board when he was programming flash via ICSP from MPLAB-X:
The board was powered through its own power supply and when he started the ICSP programming through PicKit3 an on-board high voltage power converter suddenly started operating....
Now, this converter has an enable line on pin RB10 (PIC pin 23), which is also analog pin AN10, and this line actively drives an opto-coupler. I.e. the opto-coupler LED is connected to ground with its cathode and to the PIC with its anode.
The opto-coupler isolated output drives the gate of a MOSFET which is pulled down to -12V by a 39K resistor.
This means that in order for it to activate the high voltage converter the PIC output must drive current through the LED from a high voltage level on the pin.

We were baffled about this since we understood that the PIC comes out of reset with the port B pins configured as analog inputs until running code has set the register as digital. But an input should not be able to drive the LED of an opto-coupler, right?

So is there something strange happening while programming flash through the ICSP system?
We have connected ICSP to the following pins:
ICSP pin 1: MCLR (PIC pin 7)
ICSP pin 4: PGED1 (PIC pin 16)
ICSP pin 5: PGEC1 (PIC pin 15)
There is no alternate use for these pins on the PIC.

So is there something special happening whilst programming through ICSP that can explain this behavior?
I attach a cutout of the circuit diagram of the trouble signal.

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