Two unknown cartridges

[snuci]

Hi guys,

I have a couple of cartridges that don't appear to work when I plug them in. Is there any tricks to trying them? One is definitely a UMI and the other with the switch I tried by flipping the switch (while it was off, of course) I have an eprom programmer. Can I read these these eproms? I also tried cleaning the contacts and plugging them in a few times just in case.

Any ideas on what they may be or how I can access them (if it's possible) is much appreciated.

[eslapion]

The upper photo is obviously of a VIC-1110 8k expansion which was customized by the addition of a ROM chip and switch to toggel it.

The lower board also hard 4 chips of 2k x 8 SRAM so I suspect it too is an 8k expansion but there is a fifth chip on the top and I wouldn't know what that is.

[snuci]

Thanks for the reply eslapion.

I did look up the chips and they are mostly all RAM except for the chips you mentioned. The top board has a 2532 EPROM that I have read and placed a copy here: http://vintagecomputer.ca/download/comm ... 0-2532.zip I don't know how one would figure out what the code is but if someone is interested in taking a look, I would appreciate it.

In either case, I don't see any difference when I plug these in. Both have dip switches but the VIC-1110 cartridge has more switches than what I've been able to find in documentation. The previous owner was a programmer so it might be interesting what is there.

Thanks again.

[snuci]

Eslapion,

I saw your upgrade hack in the Wiki so I took a couple of pictures of the VIC-1110 if you'd like to see how this hack was done. It may be common but I couldn't find this anywhere.

[GreyGhost]

I extracted the code with a hex editor and then ran it thru a disassembler at:

http://www.e-tradition.net/bytes/6502/disassembler.html

This is what I got from it. The code from the bin file should be mapped at $6000. This is the first few lines:

Code: Select all

                  * = 6000
6000   4C 0C 60   JMP $600C
6003   4C 3F 60   JMP $603F
6006   4C CF FF   JMP $FFCF
6009   4C D2 FF   JMP $FFD2
600C   78         SEI
600D   AD 18 03   LDA $0318
6010   85 0D      STA $0D
6012   AD 19 03   LDA $0319
6015   85 0E      STA $0E
6017   AD AF 6E   LDA $6EAF
601A   AE B0 6E   LDX $6EB0
601D   8D 16 03   STA $0316
6020   8E 17 03   STX $0317
6023   20 D6 6C   JSR $6CD6
6026   A9 00      LDA #$00
6028   85 FD      STA $FD
602A   85 FE      STA $FE
602C   A9 80      LDA #$80
602E   20 90 FF   JSR $FF90
6031   A9 FF      LDA #$FF
6033   85 16      STA $16
6035   A9 00      LDA #$00
6037   85 0F      STA $0F
6039   85 0C      STA $0C
603B   85 2F      STA $2F
603D   58         CLI
603E   00         BRK
603F   20 B6 6C   JSR $6CB6
6042   68         PLA
6043   85 05      STA $05
6045   68         PLA
6046   85 04      STA $04
6048   68         PLA
6049   85 03      STA $03
604B   68         PLA
604C   85 02      STA $02
604E   68         PLA
604F   85 01      STA $01
6051   68         PLA
6052   85 00      STA $00
6054   BA         TSX
6055   86 06      STX $06
6057   38         SEC
6058   A5 01      LDA $01
605A   E9 02      SBC #$02
605C   85 01      STA $01
605E   A5 00      LDA $00
6060   E9 00      SBC #$00
6062   85 00      STA $00
6064   20 D6 6C   JSR $6CD6

I tried attaching the file in VICE as a cart and typing 'SYS 24576' to start it to no avail. Maybe it needs to be write protected? Anyone else?

[eslapion]

The first 12 bytes appear identical to VICMON.

[GreyGhost]

Good eye eslapion. It's actually Vicmon 2.

[Kakemoms]

The upper photo is obviously of a VIC-1110 8k expansion which was customized by the addition of a ROM chip and switch to toggel it.

The lower board also hard 4 chips of 2k x 8 SRAM so I suspect it too is an 8k expansion but there is a fifth chip on the top and I wouldn't know what that is.

The fifth chip might be a multichannel relay switch. If so, the dip switch may enable the user to choose the amount of memory that is added.

[eslapion]

The fifth chip might be a multichannel relay switch. If so, the dip switch may enable the user to choose the amount of memory that is added.

The DIP switches are connected to the !CS lines for BLK 1,2,3,5

The TI chip is a form of address decoder. Why they would use such a large chip instead of a simple 74LS138, I don't know.

Ergo, what you see is a 8k expansion made up of four 2k x 8 SRAM chips with DIPs to select where to make it appear to the VIC.

These Mitsubishi chips are the same ones used in most Commodore VIC-1110 and VIC-1111

[Kakemoms]

Ah you are absolutely right. I confused the 24-pin 7240A as a newer 7240SEL.

In that respect one can put the memory at BLK 1 by setting switch 4, BLK 2 by setting switch 3.. and so on.

A picture of the backside would be interesting.

[snuci]

A picture of the backside would be interesting.

No problem. I still haven't been able to figure these out but here's a pic in any case:

UMI Back.jpg (191.67 KiB) Viewed 3320 times

[Kakemoms]

Ok. Well, the only thing I can see is that three address pins are connected to the TI 7240A, e.g. CA13, CA12 and CA11.

So its apparent that there is some simple logic in the 7240A which decides which memory chip that will respond to the memory access from the Vic-20.

E.g. $1FFF are 13 bits (8K byte), $FFF are 12 bits (4K byte) and $7FF are 11 bits (2K byte). So if each chip was 2K byte, you would need CA12 and CA13 to determine which chip to access (00,01,10,11). Since CA11 is connected it may indicate that the board was made to also function with 1K byte chips (for a total of 4K byte expansion).

Maybe eslapion has a better explanation.

As for how to fix it, it might be a cracked solder joint or fried chips. If you can find "new" memory chips you could try to swap them. Use a ohm-meter to check joints. I doubt you can find a replacement for the TI 7240A.

I also noted from the front side picture that all the dip switches are set to the same position (its hard to see if they are on or off). That might confuse the Vic-20, so try setting the BLK1 to ON and the others to OFF. Please note that if you put the memory to BLK5 it will not be available to BASIC.

[Kakemoms]

You can get an replacement of the SN44361-8Q here:

http://www.ecrater.com/p/8506623/lot-of ... sn44361-8q

It is designated 7906 instead of 7240 so it may or may not work as a replacement.

There are alot of old TI databooks here:

http://bitsavers.trailing-edge.com/pdf/ti/_dataBooks/

Maybe you can find something there.