|Meindert, guys: I think you´re gonna like this!|
Message #1 Posted by Vieira, Luiz C. (Brazil) on 22 Dec 2009, 5:45 a.m.
I must confess I had some 'second thoughts' when asking information about the HP41 system ROM versions. With no further ado:
- I took a coconut mainboard and removed the three ROM IC's; everything else was kept in place
- The HP41CV was assembled and the MLDL2000 was set in place;
- Then I programed the MLDL2000 with a CX configuration: NFL ROM set + X-FCN + Time + CX time/FCN accordingly.
It worked flawlessly: an HP41CV with a CX configuration. Of course, no clock activity and no X-Memory present.
The key point is to keep the CPLD continuously powered. In fact, for as long as the USB is plugged and active (connected), the calculator goes OK. If it is simply disconnected by the software, the calculator no longer works because the CPLD is fed according to MLDL´s J7 set (CPLD power control) or continuously through the USB port. I did not test yet, but if the CPLD is fed continuously through the HP41 batteries (J7: 1-2), the coconut may work with the MLDL2000 and without any ROM in the mainboard.
The good news is that you can use this arrangement to test your calculator and identify faulty ROM´s. And you can use the MLDL2000 to emulate the faulty ROM. In any case, this is another way to have a faulty HP41CX coconut back to life if a ROM is missing.
Now I'll try a 41CV with no RAM IC´s and point the first block address to a MLDL2000 SRAM 4K bank. I know that by simply pointing the first block address to a SRAM will cause address conflict, so I´ll program the MLDL2000 to consider the SRAM as ROM. Yep, I´ll check if the HP41 can 'see' a contiguous 4K-RAM bank, and if goes OK, then we will have all main and extended RAM at once through the MLDL2000.
Unfortunately there is no way to emulate both ROM and RAM at the same time in one single MLDL2000. The possible solutions are:
- keep ROM 0 chip in place and emulate the others;
- use two MLDL2000 (with a port extension, of course; not practical at all)
- convince either Meindert or Diego to provide such configuration trough either an MLDL2000 or a NoVRAM; this way one could run a 41CX (without a clock so far...) with external ROM/RAM.
Not a X-mas gift, instead some news to work with.
Edited: 22 Dec 2009, 5:52 a.m.