Integer BASIC Expansion Card help needed -- Chip Select

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Integer BASIC Expansion Card help needed -- Chip Select

RE: User selectable Address blocks, R, S and T.

Hey guys,

I could use a little help here.

I am working on an Integer BASIC expansion board for the Apple-1. This board has an EPROM chip

where /OE (output enable) and /CE (chip enable) are both active LOW.

On the EPROM, I tied /OE to Gnd. I have /CE connected to J3 pin 11 "S" (which is connected to the

74154 address decoder "E" via in the user selectable jumper area). I have the EPROM A0-A11 pins connected to J3 A0-A11. I have D0-D7 on the EPROM connected to J3 D0-D7. The +5v power rail on the expansion card is connected to J3

pin 22. The Ground rail is connected to J3 pin 20.

I have the upper unused Address lines on the EPROM (A12-A18 in my case) all tied to ground.
EPROM VCC is connected to +5v rail and the chip is grounded. EPROM VPP is NC (not connected).

In the jumper select area on the Apple-1 I moved "W" from "E" to "1" (as in the Apple 1 manual), so that I can use EXXX memory location for the expansion card.

In the jumper select area on the Apple 1, I have "S" jumpered to "E". So if I enter address E000

my chip should become active, right? In other words, shouldn't I see J3 pin 11 "S" go low if I

enter E000R in the monitor?

My Apple-1 jumper configuration:

W-1
X-0
R-C
E-S
Y-F
Z-D

The Apple 1 manual Note states--
UNIT IS SUPPLIED WITH:
Y Jumpered to CSF
Z Jumpered to CSD
W Jumpered to CS1 (seems that this is not the case with many Apple 1's)
X Jumpered to CS0
R,S and T ARE USER SELECTABLE CHIP SELECTS, (4k BLOCKS)

Originally I had a 7404 inverter on the expansion board because I thought the chip select at "S"

would be active high, and my EPROM wants to be active low, so I was inverting the signal. Am I

correct that I don't need the inverter, and that "S" is high until address space EXXX is active?

Are chip select jumpers "R", "S" and "T" always High unless selected? (74154 chip selects are all

active LOW according to the schematic)

For the address line configuration, I only need to address 4k bytes = 4096 (Integer BASIC is 4k).

This means I need 12 bits (A0-A11). This is why I connected the remaining address lines on the

EPROM to low.

(as an aside, The EPROM is an Atmel AT27040, so I have these extra address lines because the EPROM

is 512k... that's all I have at the moment)

thx for any tips!

John Calande
http://apple1computer.blogspot.com/

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13 bits....

Let me try this again...

I want to address 0 - 4095 which means I only need 12 bits, not 13.
1111 1111 1111

1+2+4+8 + 16+32+64+128 + 256+512+1024+2048 = 4095
Which would be A0-A11 right?

John

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Firmware card appears to be working now...

Hey guys,

I removed the 7404 wiring and chip, then moved J3 pin 11 to the EPROM /CE and it is working now.

I can now see the BASIC at E000. I haven't been able to run it yet, but check out the images:

http://apple1computer.blogspot.com/

John Calande

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um don't know much asbout the

um don't know much asbout the apple I replica , but doesnt already have integer basic built in? drops to a 6502 prompt when you hit RESET? or Ctrl=-RESET? maybe i'm wrong , dunno..

Patrick.

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John was working with a clone

John was working with a clone (Obtronix in this case), not a replica 1. As with the original, the on board ROM is 256 bytes and contains only a very simple monitor that can read memory, write memory, and transfer execution to a program at a specified address.

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Re: Firmware card appears to be working now...

servobit wrote:
Hey guys,

I removed the 7404 wiring and chip, then moved J3 pin 11 to the EPROM /CE and it is working now.

I can now see the BASIC at E000. I haven't been able to run it yet, but check out the images:

http://apple1computer.blogspot.com/

John Calande

Hi John, I've just checked on you site your progress of your Apple BASIC on an EPROM, great job!
Anyway, this is what you wrote;

Start system
Clear screen, Reset
enter: E000R
output: E000: 4C@

After this, you need to run the program at that E000 address writing "run" then hitting the return key. You will have the > basic prompt.

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Video...

Here is a video I made a few weeks ago. This is where I left off, before my keyboard died. The intention was to show the "\" after viewing the ROM, which is shown in the manual too. I entered: E000.EFFFR

E000R should run basic, in my case it appears to "freeze" and I need to reset to regain control.

http://www.youtube.com/watch?v=39JyxwhR4_k

John Calande

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Re: Video...

servobit wrote:
Here is a video I made a few weeks ago. This is where I left off, before my keyboard died. The intention was to show the "\" after viewing the ROM, which is shown in the manual too. I entered: E000.EFFFR

E000R should run basic, in my case it appears to "freeze" and I need to reset to regain control.

http://www.youtube.com/watch?v=39JyxwhR4_k

John Calande

I'm not sure but the / returns from the ACI program that calls the address FF1A (escape) in the Woz monitor.

P.S. Sorry, you don't need to "run" the basic after the E000R. I'm a bit rusty, it's 3 years from my last Apple I switch-on!

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"\"

If I remember correctly, there were additional chars, something like:

"\_E"

I don't have the ACI manual in front of me, but I think it does mention "some extra characters" but does not say which chars, maybe it's random.
I'll post again when I have a working keyboard.

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Hi all, I've finished my t

Hi all,

I've finished my third Apple 1 clone. This one happens to be the A1-Mimeo (available from www.willegal.net).
There is an image here on my blog showing the Mimeo-1 running the BASIC (firmware card).

http://apple1computer.blogspot.com/2010/05/mimeo-1-clone-up-and-running-basic.html

If you are interested, I have details on the BASIC firmware card that I designed, and finally have working, here:

http://apple1computer.blogspot.com/2010/05/apple-1-basic-firmware-card-it-works.html

thanks,
John Calande
http://apple1computer.blogspot.com/

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