ROM's again

[nama]

Ok, I finally got around to building a 2364 adaptor with the help from everyone. See here:

viewtopic.php?f=7&t=182&p=1335&hilit=2364#p1327

I have tested it by burning the ASZMIC ROM image to a 27C512 EPROM and it seems to work fine (although having my Maplin Voice card installed causes the machine to crash). Next I need to attach a switch so I can burn multiple ROMs so I can easily switch between banks. Shouldn't be too difficult.

So my question is, what ROM's are available for download and which ones will work and don't need any extra hardware?

So far I have found and downloaded ROM files for:

-Coral Basic Interpreter
-ASZMIC
-ASZMICE07 (not sure what the difference is between this and ASZMIC)
-H4th (PAL?)
-Tree4th (NTSC?)
-Z80Assembler
-ZX81_Improved
-ZX81_Unmproved
-QuickLoadSaveROM (not sure what this is, or wether it will works as a ROM replacement)

I was wondering if anyone could suggest any others? I have 8 banks to fill on my 27C512, and I figure I already have a ZX81 ROM, forth and assembler, so any other ROM's images or alternate languages would be great to include. Any help would be greatly appreciated.

Thanks in advance.
Phil

[siggi]

Hi
there is a BASIC-compatible rom with faster math routines (SG81.ROM):

http://www.wearmouth.demon.co.uk/sg.htm

And (coming with EO) a 16K(!) rom to "emulate" a Spectrum with a ZX81 (SP81.rom). But it did not work with my real ZX81

And I have my own patched BASIC roms with several patches (AUTORUN of a BASIC program according to Wilf Rigter), faster execution of GOSUB/RETURN and FOR/NEXT statements, and patches to redirect SAVE/LOAD from tape to MMC cards (using MEFISDOS).

Siggi

[nama]

Firstly, Thanks for everyones ROM image recommends.

However I am having some issues.
The ROM adaptor I built was this one:
http://freenet-homepage.de/x1541/hardware/2364.html

I have built it with a 16 position HEX switch, and I have installed a 27C512 EPROM with the following 8 images burt (and in the following order) :
ZX81_Improved
ZX81_Unimproved
Coral Basic Interpreter CBI
Shoulders of Giants (sg81)
Tree Forth (Tree4th)
Husband Forth (H4th)
ASZMICE07 (4k doubled)
Z80Assembler (4k doubled)

Installing the adaptor, and flipping through the switches I get the following:

0 X
1 BASIC
2 X
3 BASIC
4 X
5 BASIC
6 X
7 BASIC
8 (I actually saw ASZMIC load once here but crashed soon after. I haven't been able to replicate the load)
9 X
a X
b X
c X
d BASIC
e Unstable BASIC (characters shift, and crashes)
f BASIC

(the X means that the screen is blank, and nothing loads)
So as you can see, it's a little confused!!!!!
I can get a stable basic to load 6 times at 6 different positions (but I'm unsure how to test what version has loaded).

I know I have a 16 position switch and only eight images, but I would have thought that this would not have been a problem, but maybe I am wrong?? I assumed that half the switch positions would just be redundant (were two switch positions will activate the same image)
Or do I need to disconnect the A16 line??

Any help would be greatly appreciated

Phil

[sirmorris]

Hi Phil.

What switch are you using? Did you buy a board from Nicolas? Did you reconfigure it? If so, how?

There'll be more Qs before we're done, I'm sure

[nama]

Yes, I got the board from Nicolas. It came pre built as it was all he had left available at the time. I came with all traces cut between J1 thu J5, and has all SMD resistors installed.
Switch is a 16 position rotary type with 5 legs. 4 on one side of the switch, and on on the other. It looks very similar to the one shown at the bottom of this page:
http://freenet-homepage.de/x1541/hardware/2364-c.html

Thanks
Phil

[sirmorris]

Can you check the voltage levels on the chip? If you have a meter you should check the voltages at a13, a14, a15. These are pins 27, 27 & 1 respectively. See pinout here: http://www.futurlec.com/Memory/27C512-250.shtml

Note the voltages down with the switch in each of the 16 positions.

You should see:

Code: Select all

Sw.Pos    A13  A14  A15
   0       0    0    0
   1       5    0    0
   2       0    5    0
   3       5    5    0
   4       0    0    5
   5       5    0    5
   6       0    5    5
   7       5    5    5
   8      [pattern repeats from 0]

This will have to be done 'live' - it shouldn't be too dangerous if you take your time.

The only thing that I can think of which would be giving you the bizarre results is that you have the common pin on the switch wired incorrectly. Did it come fitted or did you add it yourself? Can you post a picture of the wiring?
C

[nama]

I started measuring the voltages as you said, but it wasn't correlating with your list at all. So I pulled the adaptor, and had a good look at it. Well, it seems I was incorrect in my assumption. The adaptor came to me prebuilt, with the resistors soldered, however only 3 resistors were soldered and one space (J2) was missing a resistor. Soldering in a resistor here dramatically improves things.

Now I get the following

0 ??????
1 Basic SG81
2 ??????
3 Basic SG81
4 Husband Forth
5 Basic
6 Husband Forth
7 Basic
8 ASZMIC
9 ???????
a ASZMIC
b ???????
c Tree Forth
d Basic
e Tree Forth
f Basic

If you look at the order (previous post) in which I burn things, then this ordering doesn't seem to make sense, or at least I can't figure it out. CBI and z80 assembler don't seem to load. and I can't actually tell which is the improved basic and which is the unimproved (Is there a simple test I can do).

The pins on the bottom of the switch are labeled C(the single pin by itself), 1, 2, 4, 8.
I connected them the following way:

Switch Adaptor
1 ---> J2
2 ---> J1
4 ---> J4
8 ---> J5
C ---> J3

Anyway, some improvement, just need to figure out CBI and the assembler, and also the weird ordering system now.

Phil

[nama]

Small update:
I found a ROM test program that tells you if the ROM is ok, a new ROM or old ROM.
Running it shows SG81 as failing the ROM test (that was expected).

So here is the latest list and the switch positions.

0 ??????
1 Basic SG81 (fail rom test)
2 ??????
3 Basic SG81 (fail rom test)
4 Husband Forth
5 Basic OLD
6 Husband Forth
7 Basic OLD
8 ASZMIC
9 ???????
a ASZMIC
b ???????
c Tree Forth
d Basic NEW
e Tree Forth
f Basic NEW

[sirmorris]

C would be COMMON. Should that go to J3 or ground?

I'm not surprised you only have 3 resistors as you only have 8 banks (2^3 = 8), so only the 3 address lines a13 to a15 need pulling down. The board has capacity for 1megabit, which is where the extra resistor is used - to pull on a16.

I haven't got time to check this but I will look over things later tonight.

C

[nama]

Yes, that was my understanding too. If you look at the small schematic at the bottom of this page, I believe J3 is actually GND.

http://freenet-homepage.de/x1541/hardware/2364.html

Phil