Still possible to get Minerva ROM

[Dave]

That's right. Tony put them in the box when he shipped me the mPlane PCBs. Laurence Reeves is on my FB, I'll hit him up.

[mk79]

You only need someone to burn the chips for you and they should be a plug-in replacement for the original QL ROMs.

Ah, missed your reply, Tobias. Unfortunately Sinclair had the ROM chips custom made, IIRC one chip had an inverted Chip-Enable signal or something like that so they could save another cent by leaving out an external NOT-gate. As a consequence there are no drop-in replacement for the ROMs, some form of external circuitry is always needed.

Cheers, Marcel

[tofro]

Marcel,
you might want to read my post again, then verify with the QL schematics:

Issue 5 QLs were made to run from a variety of ROM chips and combinations. The setting was made with a number of jumpers and additional components on the mainboard. The QL could then support various sizes of ROM/EPROM selected from bog standard 2764/27128 EPROM and 2364/23128 or even a single 23256 ROM chip. There's absolutely nothing special with the Sinclair ROM chips in the QL (other than that they're ROMs, not EPROMS, normally).

Issue 6 QLs no longer gave you the choice of various ROM/EPROM configurations and supported the well-known 2364/23128 combination of 48k ROM only. Still, the chips were standard 23xxx types, nothing Sinclair-specific (or how could my EPROMmer read them if they weren't?). In case you want to replace them with EPROMs, you need to adapt some circuitry because 23xxx and 27xxx are not plug-in-compatible replacements (in a nutshell, they differ in their Chip Select/Chip Enable behavior). Here is a nice article on how to replace ROMs with (a more modern, and optionally bigger) EPROM in the QL.
http://trastero.speccy.org/cosas/JL/ROM ... OM-QL.html

Tobias

[bagpuss22]

Really I need to check what version of mainboard is in my QLs are.

I know my CST Thor 8 is an Issue 5 board.

BP

[mk79]

Marcel,
you might want to read my post again, then verify with the QL schematics:

Issue 5 QLs were made to run from a variety of ROM chips and combinations. The setting was made with a number of jumpers and additional components on the mainboard. The QL could then support various sizes of ROM/EPROM selected from bog standard 2764/27128 EPROM and 2364/23128 or even a single 23256 ROM chip. There's absolutely nothing special with the Sinclair ROM chips in the QL (other than that they're ROMs, not EPROMS, normally).

Issue 6 QLs no longer gave you the choice of various ROM/EPROM configurations and supported the well-known 2364/23128 combination of 48k ROM only. Still, the chips were standard 23xxx types, nothing Sinclair-specific (or how could my EPROMmer read them if they weren't?).

I did have a look at the 23128 data sheet and you're right, it's not Sinclair specific, the level of the CS pin can be configured with these chips and Sinclair just configured them complementary on the two chips. Still, nobody will ever try to burn 23C chips and all 27C EPROMs or even EEPROMs need some kind of external circuitry, that's all I wanted to say really.

Cheers, Marcel

[Dave]

I have a crapt.... large number of the carrier boards in storage. Something like 80 or so, with IC on them but pins not attached IIRC. I'll go to the storage on Wednesday and dig them out.

[SM7I]

Dave, do you still have any MkII boards with RTC ? I want to buy. Please drop me a mail: sm7i.ham@gmail.com

The adaptor is needed to fix the adress decoding for a 64kb EPROM. In my old QLs we actually did the same by clueing an SMD NAND chip on top of the EPROM plus some flying wires. Or you can for example buy the QL-SD interface, it also comes with a daugther board that does the same, so that's a plug'n'play solution

The adaptor did not fix address decoding. It contained a registered GAL to facilitate the I2C and allow communication with the clock IC for the battery backed clock. I have 50 MK2 Minervas, but unfortunately I do not have the GAL code. The GAL was read-protected. Since it is a registered GAL and not simple combinational logic, I have been unable to recover or reconstruct the contents.

If anyone has a copy of the contents of the GAL code, I have 50 Minerva MKII with battery backed clock and I2C available immediately.

[Nasta]

IIRC the Minerva sources are now openly available, if the I2C code is present within, it could be used to figure out what addresses the GAL decoded. My guess would be the very last byte(s), but more detail is needed. Two inputs and two outputs are needed for bit-bang I2C, and since the ROM is read only, the address lines would be used for output, therefore, the two least significant ones being A0 and A1, means 4 bytes should be decoded. I suppose reading is via two data lines that can be read on any of those 2 locations. What is needed is what data lines these are and how they, and the address lines, correspond to I2C SDA and SCL lines.

[dex]

In souces here:
https://bergbland.ddns.net/downloads.htm
the subdirectory "ii", file "clock.asm".
But it is confusing.

Code: Select all

ii_clock
        move.l  sv_free(a0),a1  set buffer pointer
        move.l  a1,a4           duplicate start of transfer
        lea     cmd,a3          point to command sequence and masks
        bsr.s   ii_drive        try to get the I2C clock stuff
        move.l  a1,a2           top of clock data
        beq.s   more            if it works, great (1st byte is junk)
        moveq   #mt.rclck,d0    fall back to internal clock read
        trap    #1
        rts

ii_drive
        move.w  ii.drive,a2
        jmp     $4000(a2)

more
        and.b   -(a2),d0        use mask byte to junk msd flags bits
        moveq   #15,d1          mask for lsd and msbs all zero
        and.b   (a2),d1         get lsd
        lsr.b   #1,d0
        add.b   d0,d1           lsd + msd/2
        lsr.b   #2,d0
        add.b   d0,d1           lsd + msd*16/2 + msd*16/8 = lsd + 10*msd
        move.l  d1,(a1)+        push onto stack
        move.b  (a3)+,d0        get next mask byte
        bne.s   more            if not ending zero, keep on going

[QViewStu]

Does anybody have a scan or photo of the Mk2 Minerva board by itself ? I saw requests for the GAL code but that hasn't shown up yet although it may be in Lau's locked up Miracle Systems winchester and one day may be unearthed. In the meantime, Jon is thinking he can probably reconstruct it from memory if a photo/scan of the board is available to kick start his grey cells.

Feel free to DM me here or stuart@QVIEWIMC.com with what you have. I have a vested interest as I'd like to upgrade to the MK2 with one of the boards Dave Park has in a drawer

Stu