• Please review our updated Terms and Rules here

Powertran Cortex

That's some excellent news, Jim! Now I just need to start my build. . .
 
Tonights progress was making a lead to connect the cassette port of the cortex to the sound card in a PC.
I successfully saved a program onto the PC as a WAV file and then loaded it back into the Cortex.
Admittedly it was only a 2 line program but it's promising.

RS232 port testing next.

Jim
 
Further testing on the cassette port, recording and playing back from a PC.
The cortex connected to the MIC IN on the PC and the LINE OUT
I found i needed the record and playback volume at max.
Also, mute all mixer channels on the recorder and playback mixers except for the Wave out and the Mic in.
I found i was getting noise from the CD channel even with it's volume slider at zero, went away when muted.

The cassette interface test program in the build manual is very useful for checking the PC output level is ok and that there isn't spurious noise on the signal.
Look at pin 3 on IC67 with a scope while playing back the wav.

I've uploaded 3 wavs to my web site, are these the first Cortex programs on the net ?

http://www.quantums.info/cortex/cortex tape test.zip
This is 30 seconds of output from the cassette interface test program, alternate 0.5 second bursts of 1's and 0's

http://www.quantums.info/cortex/cortex CAS_TEST.zip
This is the program above, as per the build manual.

http://www.quantums.info/cortex/cortex C_BARS.zip
This is the program for generating the colour bars for setting up the video, again, from the build manual.

Jim
 
Last edited:
Nice update there, Jim. Looks like your post from this afternoon and mine from last night were eaten by the ether. . . Now all I have to do is to get a chance to sit down and start my own build!
 
Now that's interesting: when I logged on, all I could see were the older posts, but once I sent my first post, posts 361-363 automagically appeared! :) Good update, Jim. There are Cortex Disk programs online--lots of them are on the Powertran Cortex site. . .
 
Andy Paddon gave us copies of the software he wrote for the Cortex as wave files a while back too--I put them up on the WHT site, which may give you some additional test material. . .
 
I thought I'd already put them up, Jim--but I'll send you the zips this weekend once I find the directory I've got them in on my computer.
 
You may well have done, i could just be looking in the wrong place.
Todays mystery is:

Fitted the other TMS9902 for the RS232 port, tried to send it some data by using UNIT 2 and it hangs the system.
I altered the cassette test program (the one that generates ones and zeros) by changing the BASE value from 0180 hex to 0080 hex and it happily toggles the output of the RS232 port TMS9902.
Swapped the two 9902 chips over and the cassette port still works so i assume the chips are both ok.
The only thing i can see so far is that the program doesn't seem to use the interrupts from the 9902's.
When i use UNIT 3 (echos keypreses to the tape 9902) there are interrupts after every byte, with UNIT 2 there is just one interrupt and it hangs.

Any thoughts anyone ?
I'm re-reading the newsletters at the moment to see if there any bugs mentioned but no clues so far.

I did find that even the Cortex 2 build manual has mistakes on the circuit for the serial ports, neither of the 74LS07 buffers for the TMS9902 interrupt pins are where they are shown on the circuit. (will update with actual pins later).

Jim
 
Hi Jim,

You've certainly been busy!

With regards to UNIT 2, I think the reason it 'locks up' is that it's trying to transmit the character via the RS232 port but I don't think it can unless DSR is pulled low on the 9902. The cassette interface has this signal pulled low all the time, whereas the serial port uses it for handshaking. I just checked my Cortex <-> PC cable and I have pins 6 and 20 connected on the Cortex end. Worth a try.

By the way, I believe a Graph-Rubout forces a 'UNIT 1' so it can get you out of that situation without having to Warm Start or Reset.

Dave.
 
Last edited:
Hi Dave,
Many thanks for that, you were indeed correct that it wasn't working because DSR wasn't low.
I missed that when checking the control lines.
But linking pins 6 and 20 didn't fix it, at least not initially.
After linking the pins and finding DSR still not low on the 9902 i realised that it was because i hadn't actually linked pins 6 and 20 on the connector.
When i assembled the pcb i fitted a 25 way plug (with pins), like the serial port on a PC, i'd not spotted that the Cortex used the opposite.
So i'd not been linking the pins i thought i was, with the wrong gender of connector the pin numbers were from the other end of the connector.
Allowing for this it now works.
Not looking forward to removing the connector from the DS PTH board though, probably use my usual method of drill out the rivets and then cut the housing up with a pair of wire cutters until i can remove each pin separatly.

Thanks for the clue that pointed me in the right direction though.

Next thing (the connector can wait for a while), the FDC.
Also, wonder why the speaker does a random beep every min or 2.

Jim
 
Argh, why does IE8 have to have the little close button that appears in the corner of each tab.
Had a big long message typed here and then hit the close when switching tabs :-(

Basically, both the TMS9909 i had (one from Ebay, one from Jim) are fake chips.
But the 2 off TMX9909 i found on the net appear to be genuine.

Will retype all my findings tonight.

Jim
 
Jim Hearne said:
Basically, both the TMS9909 i had (one from Ebay, one from Jim) are fake chips.
But the 2 off TMX9909 i found on the net appear to be genuine.

Jim
Click to expand...

That sucks. I bought two for $40 from UTSource on eBay a few months ago. I thought it was odd they were TMS9909 rather than TMX9909 but I haven't tried them. Grrrrrrr.
 
Fake TMS9909 and real TMX9909.jpg
UTsource was where one of mine came from, sorry.
I've just sent them a snotty email but i bought it back in May so probably not much else will happen.
Looking at them now, what i assume are the date codes are totally wrong, one is 9808 and the other 0440, way too late for TMS9909 production.
The TMX9909 has a date code of 8314

If you want to do a test of yours, hook up 0V to pin 1 and 5V to pin 23, the good chips draw about 110ma (Spec says 150ma nominal), the fakes are 5ma and 31ma.


Jim
 
Last edited:
Actually I just checked what I bought. I got one TMS9909NL which looks kinda dodgy like the ones above and a TMS9911NL which does look pretty good, with a date code of 8745, but who knows. I'm now pretty reluctant to try them in case they blow something up! I appreciate the current measurements, though.

Dave.
 
I have a small number of TMX9909s as well as the TMS9909s I was suspicious of (I sent the one Jim has as a test object). Thanks for the confirmation of my suspicions, Jim! I got the TMX chips from a reliable US source, so they "should" be good. I think I bought 7-8 of them. Right now the one chip I don't have a good stock of are the 9911s. About the only regular source of them I see is Little Diode on EBAY, and they're a bit expensive there. . .
 
My TMX9909 came from the US as well, just from a list of spare chips somebody had on their web site, i think i had the last 2 though.
The TMS9911 i bought from Little Diode , they did give me a better price than they had on Ebay but it was still expensive (34usd).

I've fitted all the floppy chips and connected up a pair of old BBC floppy drives.
Got to the stage where it appeared to be trying to read the floppy but something in the drive decided to put gunk all over the disk surface so need to look at that.
Also not made a Cortex boot disc yet, got to get the PC to do that.

Jim
 
Last edited:
You must log in or register to reply here.
Back
Top