68000 Halted on Starter
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Author:  moahrs [ Sun Feb 17, 2013 2:47 pm ]
Post subject:  68000 Halted on Starter

If any1 know one site or place that I can find this response.

I maked a project using a 68000... But I have tested all signals, all and I not understand...

When I turn on my project, the 68000 goes to halted (pin HALT is lower). I have tested BEER pin and is HIGH.

When I put 58Hz (for test, in this frequancy, shows that 68000 dont works) but pin halt is high (1).

Any1 know another cause (out pin beer) that can halt 68000 in error ?????

ty a lpt

Author:  clive [ Mon Feb 18, 2013 7:40 pm ]
Post subject:  Re: 68000 Halted on Starter

What is happening with AS, and DTACK?

Do you have a schematic?
Do you have a logic analyzer?

Author:  moahrs [ Tue Feb 19, 2013 12:05 pm ]
Post subject:  Re: 68000 Halted on Starter


Ty for response.

I See one light in the end of road, and now, I discovered my problem, in my code, in first 8 bytes, 4 to SP and 4 to PC, in the SP, I have putted 0FFFFFF (odd byte). Then, I putted 0FFFFFE (even byte) and halt dont go to low(0) at turn on my project any more.... But still a bit confuse... Below, my program for test, is very simple.


       org $0
       dc.l 0x0FFFFFE           ; SP address
       dc.l 0x0000400           ; PC address
       org $0400
       clr.b     D2             ; 0 to D2 (counter)
       clr.l     D3             ; 0 to D3 (counter to wait)
       and.w     #255,D2        ; verifiy se counter is 0xAA (count from 0x00 to 0x99 step 11)
       cmp.w     #170,D2
       bne.s     main_4         ; if not, jump to display counter
       clr.b     D2             ; else, 0 to D2
       and.l     #255,D2        ; display counter at 7 segments display with buffer and latch
       move.l    D2,_display
       add.b     #11,D2         ; add more 11 to counter
       clr.l     D3             ; initialize counter to pause
       cmp.l     #4095,D3       
       bhi.s     main_8
       addq.l    #1,D3
       bra       main_6
       bra       main_1         ; return to main bloxk

       dc.l      $0400000

But I think that I still confuse with architeture of 68000. I worked for many time with Z80 and others, when the memory organization is diferent of 68000.

After I compiled, generated the .HEX I use a software named mot2bin, for transform .HEX in .BIN, and I write in my 2 flash memory 29C020 (256Kx8). The even byte (such as 0x00000, 0x00002, ...) I put in D8 to D15 (activated with UDS), and the odd byte (such as 0x00001, 0x00003, ...) I put in D0 to D7 (activated with LDS).

For now, the project dont goes to halt (0), but it dont do what I need.

Anexed, my project in PDF.

Ty for help
Moacir Jr.

Author:  lee [ Tue Feb 19, 2013 11:31 pm ]
Post subject:  Re: 68000 Halted on Starter

Well you seem to have got the byte order right.

What is your address map?

I guess you have the FLASH from $00000 to $3FFFF, unless you're using a MAP circuit, but where is the RAM and how big is it.

You should set the initial stack pointer to the next address after the RAM. So if the RAM goes to $7FFFF the initial stack pointer should be $80000 as the pointer decrements and then saves the value.


Author:  moahrs [ Wed Feb 20, 2013 11:05 am ]
Post subject:  Re: 68000 Halted on Starter

Oh yes, sry for forgoted.

Map Memory:
$00000000 - $001FFFFF - Flash Memory
$00200000 - $003FFFFF - Not Used (Future Expansion)
$00400000 - $005FFFFF - Peripherals
$00600000 - $007FFFFF - RAM Bank Memory Select and Future Expansion
$00800000 - $00FFFFFF - RAM Memory (2 Banks of 8MB)

I am using DRAM, one old module EDO RAM 16MB. I am not tested yet. I am will just test today, if I have time.

In my program, I discovered the problem. I messed in definition of "_display". The "_display" was at address $0434 and not at $00400000. I changed to correct address, and the 7 segments display showed my test.... Still have a litle bug that after +/- 2 minutes executing, the board freeze (or the program stop), and the voltage at halt pin is +/- 1.46v. I searched for problems in signal, wires and other, but is all OK. I still searching.

Moacir Jr.

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