Search found 23 matches

Return to advanced search

Website updated

I finally got around to updating the website on this project: http://mini-altair.tripod.com/ (Ad blockers and popup blockers are recommended.) It now has pictures, screen shots, schematics and source code. The disk emulator should be usable on the Altair Micro connected to the expansion port or on a...
by xprt
Sep Tue 28, 2010 2:41 am
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: Floppy Disk Emulator
Replies: 2
Views: 6176

Yet another Altair 8800 PC

This guy built a small size Altair 8800 front panel and put it on an Altair 680 case with a Core i5 motherboard inside:

http://galacticstudios.org/component/content/article/2-electronics/14-minialtairpc

Looks nice.
by xprt
May Sat 08, 2010 7:28 am
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: Yet another Altair 8800 PC
Replies: 2
Views: 4276

Re: Floppy Disk Emulator - CP/M

I increased my RAM to 64k and got CP/M working. I found that the Altair32 CP/M 2.2 BIOS inexplicably resets the UART after it outputs the welcome message. This clears the baud rate clock settings, number of stop bits settings, etc. and prevents the UART from working. This isn't a problem for the sim...
by xprt
May Thu 06, 2010 5:06 pm
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: Floppy Disk Emulator
Replies: 2
Views: 6176

Floppy Disk Emulator

http://farm3.static.flickr.com/2687/4515421379_591c695b37_t.jpg I've built a floppy disk emulator using an SD card. It is register compatible with the MITS Altair 88-DCDD floppy disk interface. This allows it to run Altair Disk Basic and Altair DOS directly without modifying the code. The hardware ...
by xprt
Apr Mon 12, 2010 6:22 pm
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: Floppy Disk Emulator
Replies: 2
Views: 6176

Hi Vince, Actually you should refer to the 8080 Assembly Language Programming Manual. It has detailed descriptions of each instruction. It says DAA is the only instruction that uses the auxiliary carry. SBB does not use auxiliary carry but does set or clear it. Here's a link: http://www.tech-systems...
by xprt
Feb Wed 17, 2010 7:13 pm
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: Third and final attempt at the Altair project
Replies: 73
Views: 113451

I created a webpage on this project:

http://mini-altair.tripod.com/index.html#top

Sorry about the ads. Free sites aren't free.
by xprt
Nov Thu 05, 2009 8:16 pm
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: AltairPC clone?! runs BASIC
Replies: 12
Views: 54436

OK: Source Code (c code) Schematic (pdf) To add LEDs involves adding buffers to the address, data, and status lines. Adding switches could be done in various ways. One way would be a switch array, with the PIC reading the switches. I left the 8 address lines connected to the PIC, but they are not us...
by xprt
Aug Sat 08, 2009 11:49 pm
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: AltairPC clone?! runs BASIC
Replies: 12
Views: 54436

I did some re-wiring to use the READY line using this circuit: http://farm4.static.flickr.com/3479/4045836394_45f02682c0_o.jpg When I raise the RUN line, this circuit will drop the READY line on the first CLK edge after ALE goes low. This stops the 8085 at the right time: when the address is latched...
by xprt
Aug Sat 08, 2009 12:48 pm
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: AltairPC clone?! runs BASIC
Replies: 12
Views: 54436

The datasheet says S1 and S0 are unspecified when HOLD is active. You probably have to use the READY line instead of the HOLD line. When you go from RUN to STOP you can lower READY at the beginning of each cycle and then you have as much time as you want to check the S1 and S0 line for an opcode fet...
by xprt
Mar Tue 24, 2009 1:10 am
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: AltairPC clone?! runs BASIC
Replies: 12
Views: 54436

I confirmed that 8K BASIC and Extended BASIC also run. This confirms that the sense switch register is working since these require different switch settings than 4K basic. I've tried several BASIC programs like startrek for example. Here's the schematic: http://farm4.static.flickr.com/3430/338350010...
by xprt
Mar Mon 23, 2009 3:06 am
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: AltairPC clone?! runs BASIC
Replies: 12
Views: 54436

That looks good. By the way, I did use the S1 line for the 6850. The 6850 has an E input and an R/W input. The R/W input has to be set before the E input. The S1 output is set by the 8085 near the beginning of the machine cycle and is valid through the rest of the cycle. As the datasheet says, it ca...
by xprt
Mar Sun 22, 2009 11:57 am
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: Third and final attempt at the Altair project
Replies: 73
Views: 113451

Your bus transceiver should be enabled when the RD signal is active (low).
You shouldn't use the S0 and S1 signals at all.

You want BNK2 = 0 when
A8..A15 all = 1,
and IO/M = 1,
and RD = 0,
or BANK2 = 1

BNK2 = !(A8 * A9 * A10 * A11 * A12 * A13 * A14 * A15 * IO/M * !RD + BANK2)
by xprt
Mar Sun 22, 2009 2:51 am
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: Third and final attempt at the Altair project
Replies: 73
Views: 113451

Yes. The bootloader image is essentially stored in the PIC's program ROM (actually flash RAM). The PIC just copies it to the external RAM. As you probably know, to load BASIC into the Altair without a ROM card, you had to enter a tiny program into RAM with the front panel switches. This bootloader p...
by xprt
Mar Wed 18, 2009 5:45 pm
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: AltairPC clone?! runs BASIC
Replies: 12
Views: 54436

AltairPC clone?! runs BASIC

I couldn't stop thinking about the 8085 running Altair basic, so I built one. I tried to do the simplest thing I could think of (meaning simplest hardware, minimum amount of programming). So I took the 8085, a RAM chip and the 6850 and used a PIC microcontroller as the bootloader to pre-load the RAM...
by xprt
Mar Wed 18, 2009 2:34 am
 
Forum: Venues, projects and off topic stuff - NO SPAM
Topic: AltairPC clone?! runs BASIC
Replies: 12
Views: 54436
Next

Return to advanced search

cron