Making kickstart swapswitch for A1200

[Loedown]

Originally Posted by Zetr0

@loedown

indeed, I have been toying with building a 2/4MB Flash Ram adapter, one that could be programmed and switched internally by the A1200 from software and or keypress.

With a 3.1 fall back or somthing like that.

This would be a great little bit of fun for prototyping 2mb kickstarts and maybe kickstart replacements .....

>

Not to mention programming on the fly, no need for the whole program UV cycle.

[Toni Wilen]

Proper commercial Amiga flash replacement should have following (which would be much more useful than simple ROM switcher):

- socket for original ROM, can be sold empty and can always boot, even _when_ (not if) you mess up the flash data. No need for programmer, also prevent socket damage.
- SMD flash chip under the ROM socket (for example 29F160 which is 5v compatible and still available)
- solder pads for upper address lines (1M/2M hacks)
- solder pads to switch between ROM and flash (see below)
- SMD GAL or CPLD also under the socket that handles output enable/chip select signals + solders pads for Gary/etc connections + possible switch from real ROM to flash logic if there is space, maybe other "nice to have" logic too (probably requires a CPLD)
- must be compatible with all Amiga models (two identical adapters used in 32-bit Amigas, must fit in A1200)

I would buy 10 or so immediately

Software would be easy to do, I have even thought about flashing from disk ("a1000" emulation), serial or even using Amiga Explorer, as long special "boot block" is intact in flash)

[Zetr0]

Hiyas Calgor

Originally Posted by Calgor

@Loedown

Yep, just a matter of how much space spare.

@Zetr0

Ah thanks diagrams make it easier.

Truly welcome I love making diagrams

Originally Posted by Calgor

BUT in your diagram it says that to select the high address range 1MB ROM, instead of my understanding (and as per the guy in the link I had posted) that it is only the uppermost address pin (A18) that needs to be set high........ your diagram says that A16 and A17 should be Hi, and A18 Lo.

Yes, I think I made a boo-boo with the 1MB Kickstart address let me check

Originally Posted by Calgor

Are you sure that is correct? I thought that A18 Hi would be for the entire upper half, then A17 would be for smaller half within range selected by A18, and so on for the other address pins.

lets see

Location - location location

it would seem I got caughtup with partitioning the 4x 512KB rom assertions

I shall sort out the assertion map and do some base location calcuations on the end of it after diiner =)

[Zetr0]

probably having a blond moment here -

27c800 A1200 kickrom partion

hex loction starting position (off sets) -

[0x 00000 - 3FFFF] kickrom 1 - Size = 262143 - BIN [ 0000 0000 0000 0000 0000 ] - (A17[LO]) - (A18[LO]) 
[0x 40000 - 7FFFF] kickrom 2 - Size = 262143 - BIN [ 0100 0000 0000 0000 0000 ] - (A17[HI]) - (A18[LO]) 
[0x 80000 - BFFFF] Kickrom 3 - Size = 262143 - BIN [ 1000 0000 0000 0000 0000 ] - (A17[LO]) - (A18[HI]) 
[0x C0000 - FFFFF] Kickrom 4 - Size = 262143 - BIN [ 1100 0000 0000 0000 0000 ] - (A17[HI]) - (A18[HI])

The upper 512KB of the ROM (0x80000) is where you want the second 1MB Kickstart, which if I am right should be -

(A17[LO]) - (A18[HI])

This is as you stated above (sorry about that), hmmm it would seem I am having endian issues relating to bit-fields in selecting pin location of the chip..

need... more.... coffeee...


Update

I have corrected the assertion map, its should be right now.

[Calgor]

A webpage with simple easy to understand descriptions of pull-up resistors - the diagram to set an input to hi or lo is exactly the same as Loedown's diagram (post 5).

http://www.seattlerobotics.org/encod...97/basics.html

If I use that circuit (one for each ROM) then I only need a DPST as the switch will either open or close the circuit.


The alternative is per my diagram (post 14) which requires a DPDT as the switch will either connect the address pin to the resistor and +5V or connect it to ground.

Any comments as to which approach is better?

[Zetr0]

Upper 1MB Address - VCC - 47K - Pin 1 (HIGH) U6A and U6B
Lower 1MB Address - GROUND Pin 1 (LOW) U6A and USB

[Loedown]

Originally Posted by Zetr0

Upper 1MB Address - VCC - 47K - Pin 1 (HIGH) U6A and U6B
Lower 1MB Address - GROUND Pin 1 (LOW) U6A and USB

Should the resistor not be 4K7, not 47K, I know it's just a pullup?

[Zetr0]

@loedown

Great spot on the typo, sorry about that chaps! 4k7 (4700 ohms)

lol 47,000 ohms would be a TAD too much lol!


@calgor

the circuit that Loedown put up is perfect for your project.