Hi,

Using the same crystal should not be a problem. Only then you should use an oscillator or make one with a crystal and an inverter. But do not use one of the inverters on the ST7s, and of course not several of them. And in this configuration, do not send the 12MHz from RLink either, as you already have a clock.

For sharing the ICP connector it is not so easy. I have never done this before and never received such a request, but it should be feasible. Below is how I would do it. I cannot guarantee that it will work from the first try, so make sure that you validate the process before launching the board in mass production...

For entering program mode, the RLink must be able to drive the RST, ICCCLK, ICCDATA and VPP/ICCSEL pins. The simplest solution I see is to choose one of these lines and use jumpers or switches on your board to disconnect all but one of the ST7s from the associated signal on the RLink. I would say to use RST, but that will not work if you have a global RST on the board that connects all RST signals. (push-button...) In this case, I would use VPP/ICCSEL, as this line happens to rise at 12V and it's better not to overload it. But it should also work with ICCCLK or ICCDATA.
The best would be to disconnect all these lines, but then the jumpers would take more space than four ICP connectors. ;/

Finally, you must be sure that once programmed, an ST7 will not interfere on the RST, ICCDATA and ICCCLK signals, which would prevent you from programing the 3 other ST7s.

In the end if it still doesn't work, you might also want to consider another option: purchase socket boards from ST and program the ST7s before soldering them. That forbids reprogramming, but saves you the space for even the single ICP connector.

Please let us know what you try and how it goes, as other people might have the same kind of problems.

Best Regards,

Vincent