[Coco] Kip's Single Board Computer

[camillus]

Hi, Kip,

A minimum setup would be cpu, crystal or resonator, ,eprom with startup vector at &HFFFE and &HFFFF.

The vector should have a JMP (&H7E) to &H4000.

&H4000 is just a range between &H000 and &HFFEF
 
| FFF0H to FFF1H |Reserved by Motorola | | FFF2H to FFF3H |SWI3 instruction interrupt vector | | FFF4H to FFF5H |SWI2 instruction interrupt vector | | FFF6H to FFF7H |Fast hardware int. vector (FIRQ) | | FFF8H to FFF9H |Hardware interrupt vector (IRQ) | | FFFAH to FFFBH |SWI instruction interrupt vector | | FFFCH to FFFDH |Non-maskable interrupt vector (NMI)| | FFFEH to FFFFH |Reset vector

The eprom should have at &H4000 the opcode &H12 (NOP) and at &H4001 BRA 0x10000001 (-1).

You have to check the branch operand, because i'm sure it is a byte but not sure it is the first bit to set for negative = back branch or positive is forward. 0b00000001 = +1

BRA can do -128 and +128 ( 255 places  max  0=n/a ).

hope I make any sence.

This can be easy made on a small breadboard.
cb

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On 9/7/2015 8:51:07 PM, RETRO Innovations <go4retro at go4retro.com> wrote:
On 9/7/2015 5:26 PM, Kip Koon wrote:
> Hi Jim,
> Thanks for looking at my Kipper SBC. I am also at a standstill as I so far have not figured out what is keeping the CPU from running.
Does anyone have a schematic of a minimal 6809 setup I can test?
Something like a hardwired NOP on the data bus?

JIm


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