Stuart

What Chris just said above. For the exact keystrokes needed, see the thread [http://atariage.com/forums/topic/237015-help-troubleshooting-repairing-ti-fdc-and-ti-32k-mem-cards] and read post #25.

Have you got a MiniMem cartridge? That make it easy to test that the DSR is being read correctly.

I think that should be 'TI senior management/marketing must always choose "b"'. TI engineers left to their own devices developed the 9995-based Powertran Cortex, which includes several option "a"'s. Stuart.

As JamesD said above, the functionality is good for self-modifying code. An instruction might be LI R0,>1234 now, but code can over-write the value >1234. You might do this in a loop perhaps, incrementing what was the value >1234, and with a JEQ to break out of the loop when the value rolls over to zero.

That's my quota of great ideas for this year used up.

I have a copy of the "Atari Inc - Business is Fun" book for sale on eBay. http://www.ebay.co.uk/itm/301649881951 Starting price is £5.00, plus £4.00 postage. Will deliver to the UK only. Stuart.

Have doubts that the schematic will work as shown. Particularly as the transistor appears to be connected across the power supply! So what is it you're trying to do again? When the joystick is scanned (pin 7 goes low), you want to feed the output of your IC to the joystick right line (pin 9)? Instead of using a transistor which needs bias and current limiting resistors, how about using a 74LS125 (Google for the datasheet). Connect joystick pin 7 to the C input, your IC to the A input, and the Y output to the joystick pin 9. The Y output is floating when the C input is high, so it shouldn't affect keyboard scanning. I think.

Thanks Matthew. I'll see about an F18A tall pin order. All credit for the PCB goes to Paul "pnr".

Yes, that's how I usually connect up my TI when I use it. Got a bog-standard tuner card from Novatech. However, I've got the type of PAL RF modulator that has a metal box where you can pick off a composite signal to feed to the tuner card, rather than using the aerial output.

It's a further development by Paul (user "pnr" on here and the Powertran Cortex forum [http://www.vintage-computer.com/vcforum/showthread.php?15580-Powertran-Cortex]) of my TMS9995 breadboard system. Basic specs: -- TMS9995 running at 3 MHz, with no wait states when accessing RAM. -- 32K EEPROM. -- 512K RAM accessed through a 74LS612 memory mapper. -- Socket/interface for an F18A. -- TMS9902 serial interface, connected to either an on-board or external TTL serial <-> USB interface module. -- Single-step instruction circuitry. -- CF card interface for mass storage, with FAT format software driver. -- Most 'glue logic' incorporated in reprogrammable GAL. -- Circuit to provide a write-protected area of RAM, for a protected UNIX kernel (I think!). -- 8-bit CRU output latch, with 5 outputs currently spare. -- Couple of status LEDs. It will run: -- Cortex Basic (either from EEPROM or disk). -- Marinchip Disk Executive (MDEX) - disk operating system for computers based on the TMS99xx processor and ported to the Powertran Cortex in the early 80's. Includes text editor, assembler, word processor, Forth, Pascal, Meta compiler writing language. See [http://www.powertrancortex.com/documentation.html]. -- LSX Unix [http://ruizendp.websites.xs4all.nl/screenshot3.png]. In development is a port of the Texas Instrument Network Operating System (NOS), which features: -- Multiple storage units mounted as Volumes (4 floppies, RAM disk, Hard Disk). -- Directories. -- Users, Groups, Access Rights. -- Interrupt-driven I/O. -- Time/Clock. -- Automatic directory and file creation, expansion and fragmentation. -- Script files. -- Easier file copying (file/directory/volume). -- File paths by volume name e.g. MYNOS:utils/source/test.asm where MYNOS is the volume name of, say, a floppy. The best source of further information is probably the Powertran Cortex forum - [http://www.vintage-computer.com/vcforum/showthread.php?15580-Powertran-Cortex]. Go to the last page and read backwards. It's all being done as precious hobby time permits of course! Stuart.

Hi Matthew. I'm looking at how we can fit the F18A to the Mini Cortex board. Photo attached. So the F18A is going to sit across the top of the CF adaptor board, which itself is plugged into a socket. The tops of the pins on the CF board sit 10mm above the PCB. We'd need maybe 2mm clearance above that. I don't think the tall pin version of the F18A is going to raise it high enough? What are our options? Are you able to fit even taller pins to the F18A? Or maybe stack some pin header strips to raise it high enough? Or use a wire wrap socket with the pins cut down to raise the socket off the PCB? Any suggestions? Thanks, Stuart.

Could always try that age-old trick of looking at the component location diagram in the TI-99/4A technical data manual (on ftp://whtech.com/) to get the component ID, then finding that on the circuit diagram. If it's from the row of caps immediately above or below the VRAM, it's 0.1uF.

Well, one 'use' is to swap the values in two variables without the use of a third variable. This screws my head every time I think about it. Try this: 100 X=1234 110 Y=5678 120 PRINT X,Y 130 Y=X XOR Y 140 X=Y XOR X 150 Y=X XOR Y 160 PRINT X,Y

I'd say that indicates a problem with address bit A14. This is buffered onto the board by U2 (74LS244) and feeds the two EPROMs, the FDC chip, U23 (74LS259) and U22 (74LS251). The EPROMs are probably OK as swapping between the 40 track and 80 track versions makes no difference. The FDC chip you've tried in a different system and that is OK. I'd try removing U2 and fitting a socket, but before you pop in a new chip, measure the resistance between the EPROMs pin 7 and GND - is it a dead short? If yes, has the board ever worked since fitting the sockets for the EPROMs? If no or unsure, it's possible that fitting the sockets has shorted that pin. It's possible but less likely that U21 or U22 are shorting that address line - could try replacing those as well. Wouldn't worry about the warm chips at the moment. Sort out the memory problem first. They might just run warm normally anyway.

What I meant - and I wasn't particularly clear - repeat what you done with the MiniMem cartridge, but after the "M4000", keep on pressing <Enter> to display lots more bytes from memory, rather than just 6 bytes from the earlier test. Do 20 bytes and report back what you see. The two chips that are warm - is the voltage regulator hot as well? Could they just be getting radiated heat from the regulator?

Matthew, the version of the F18A with the longer pins - how much higher does it sit above the board? (Couldn't see a picture of that version anywhere.)

Compare some more bytes - they should be as below. But it looks as if what you're seeing is each pair of bytes being repeated? Which I think points to a stuck address bit A14? Do you get the same (repeated bytes) with the 80 track EPROMs? DATA >AA02 standard header mark, version 2 DATA >0000 no programs DATA >4044 power-up chain ptr DATA >0000 programs chain ptr (none) DATA >404A DSR chain ptr DATA >4010 subprograms chain ptr DATA >0000 ISR chain ptr (none) DATA >0000 DATA >4016 link to next subprogram DATA >5B38 address of that one

(1) Insert MiniMem cartridge and switch on console. (2) Press any key at the master title screen then select option (2) Easy Bug. (3) Press any key. (4) Type C1100<Enter>1<Enter><full stop (.)> (5) Type M4000<Enter><Enter><Enter><Enter><Enter><Enter><full stop (.)> It should now be showing the contents of memory location >4000 to >4005. These should be >AA, >02, >00, >00, >40, >44. Is that what you see?

It's going to be around for a good few years yet. http://www.pprune.org/tech-log/380212-avionics-lead-free-solder.html Places like Jameco have it if you can't get it locally.

I was meaning just try this on the HSKOUT line to see if it improved the "the RPi keeps on sending data" problem. If it made no difference then nothing lost. If it did improve things then it might point to a problem with the level shifting IC circuit and you could investigate further.

I think you need a DSR on the card with a power-up routine that takes control and doesn't return back to the console software. The card would need to be on a CRU address higher than all the other cards so that their power-up routines (if any) get run first.

Ah, you're absolutely right. I've been looking at the values for the 2.5 MHz processor. <blush>

HSKOUT is generated by the TI using 5V logic, and needs to go to the RPi using 3.3V logic? Try doing the voltage conversion for this signal using a simple resistor potential divider rather than an IC. [http://www.savagecircuits.com/attachment.php?attachmentid=286&d=1372033234] Also try putting a 22 Ohm resistor in series at the TI end (after the potential divider) to minimise ringing on the line if it's a long cable. May make absolutely no difference but simple to try.

I remember seeing that nearer the time Michael, and couldn't actually seem to get the values in the diagram to agree with the values from other sources. For example, for 1200 Baud, the RS-232 DSR gives a value of >015B, as does the TIBUG listing for my TM990 board. But looking at all combinations of clock divider and multiplier in that diagram, none of them seem to have a value reasonably close to that?

The nanoPEB RS-232 DSR may well be based on that in the TI card - a disassembly of which is available here: [http://www.unige.ch/medecine/nouspikel/ti99/rs1.txt]. I'd start working through both and you should be able to find the baud rate table and the data to load into the TMS9902 - this starts at label A40A6 in the listing. Once you've found that in the nanoPEB, you can recalculate the 9902 data needed for a different console clock rate using the information on this page: [http://www.unige.ch/medecine/nouspikel/ti99/rs232c.htm#Operating9902]. Stuart.