I thought I'd best start a new thread for the Microchip parts versus the discussion here
https://www.eevblog.com/forum/fpga/programming-(non-jtag)-max7000-devices about the MAX7000 devices.
What I'm wanting to be able to do is set the security fuse on Microchip ATF150x series parts, and then be able to erase and reprogram them using a JTAG programmer.
For JTAG programming I have been using the Microchip ATDH1150USB, and that works great for programming the parts in system. On designs where I've used some or all of the JTAG pins for general I/O, I've been careful to lay the board out in such a way that I can safely apply +12V to the OE1 pin - this allows the JTAG interface to be re-enabled for re-programming.
What I've not been able to do though is secure the design via the security fuse. Or at least I've not been able to reprogram a chip afterwards using the ATDH1150USB programmer. Even with +12V applied to OE1.
Thus I'm trying to work out the secret to this. Using my Xeltek 6100N with TQFP44 adapter I can secure a chip, and erase it, and reprogram it and re-secure over and over. But thats not a practical solution when the chip is soldered to a board. I'm also very curious as to how it does this and will have to put the logic analyser on it no doubt.
I noted that Xeltek do a dedicated ISP programmer (the IS01), so I sent them a support email to query whether this is possible using the IS01. I havent got to the bottom of that yet (they didn't answer that particular question) however they did send me information on the connections required for JTAG progamming ATF150x (attached as I'm unsure how to attach images inline).
I note that they do indeed include the OE1 pin (Vpp) on their header so I'm hopeful that this programmer might be able to do it. I've asked again the specific question as to whether it can reprogram a secured device so I'll see what they say. Its not a cheap programmer, but if it can do it then I may just have to get one. I'll report back my findings.
EDIT : For projects where the JTAG interface is dedicated (not used for general I/O) you can happily secure the device and reprogram over and over with the ATDT1150USB without the need for voltage on OE1 at all. The issue is when the JTAG has been reused for IO, and security enabled.