Tektronix Tek7854 free download

File name Tek7854.txt

From: [email protected] (Pentti Haka) Subject: Re: TEK 7854 Oscilloscope ROM board needed Date: Mon, 26 Apr 1999 06:54:52 GMT I found the ROM images. But, as usual, I have not documented anything, and do not exactly remember what it was that I did. So the following is based on vague memory: The board contains three types of chips: - the basic ROM set, 16 kwords, at address 0 - a patch EPROM set, 2 kwords, at address 0x9000 - an FPLA that maps the patched addresses to the patch EPROM instead of the base ROM Normal ROM board accesses go to the base ROM. When a part of the program in the base ROM has been revised (patched), the FPLA directs memory accesses to the patch EPROM instead. The FPLA only decodes the patched addresses, and the actual patch code resides in the EPROM. A typical patch is a few words only, inserting a jump instruction for example, which then causes a jump to the EPROM address space where the actual patch code resides. The patch EPROM contains three types of data: 1) the patch words, that the FPLA inserts into the instruction/data stream to cause jumps/calls to the patch code, 2) actual patch code (subroutines etc) which are directly executed from the patch EPROM and 3) part of the "normal" operating system code also seems to reside on the patch EPROM. At least in my scope, if I disable the patching mechanism altogether, the scope does not work. This would indicate that the base ROM set alone without patches is not a working version. When the ROM board contents are read out using the edge connector bus, the patches are automatically "visible" and are already contained in the ROM image, so the patch FPLA must be disabled when the new EPROMs burned from the image are installed (your FPLA probably isn't the same version as my ROM image, so the patch addresses decoded by the FPLA would be wrong anyway). However, you must still have the correct version of the patch EPROM installed, since the EPROM also seems to contain "normal" code, in addition to the patch data and code. I have attached all files I found. 7854MSB.ROM and 7854LSB.ROM are the straight binary ROM images from the base ROM, without patches. This is what you would get if you'd read the ROM contents from each ROM chip individually. 7854MSB.PAT and 7854LSB.PAT are the straight binary ROM images from the base ROM, and they include the patches. This is what you get when you read out the board contents via the edge connector bus. 78549000.LSB and 7854-9F9.MSB are the straight binary patch EPROM images. Do not ask why I have named the files like that, I do not remember. So what you should do is: Burn 7854MSB.PAT and 7854LSB.PAT into 16 kbyte EPROM chips and substitute these for the original ROM chips, using the technique of your choice (I hope you have the service manual) Burn 78549000.LSB and 7854-9F9.MSB into 2 kbyte EPROMS and plug into the patch EEPROM sockets Disable the patch FPLA, so that all accesses in the range 0-0x7fff will access the two new bas