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Powertran Cortex

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    That's some excellent news, Jim! Now I just need to start my build. . .
    Enter My Mind At Your Own Risk!


      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.



        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 ?
        This is 30 seconds of output from the cassette interface test program, alternate 0.5 second bursts of 1's and 0's
        This is the program above, as per the build manual.
        This is the program for generating the colour bars for setting up the video, again, from the build manual.

        Last edited by Jim Hearne; October 23, 2012, 01:17 PM.


          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!
          Enter My Mind At Your Own Risk!


            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. . .
            Enter My Mind At Your Own Risk!


              Same happened to me, once i posted my last message my previous message and your reply both appeared.



                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. . .
                Enter My Mind At Your Own Risk!


                  Do you mean you are going to upload them, or that they are already there (in which case i can't find them).

                  Many thanks,



                    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.
                    Enter My Mind At Your Own Risk!


                      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).



                        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.

                        Last edited by tms9995; October 26, 2012, 11:49 AM.


                          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.



                            Originally posted by Jim Hearne View Post
                            Also, wonder why the speaker does a random beep every min or 2.
                            It's not the self destruct countdown I hope. ;-(


                              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.



                                Originally posted by Jim Hearne View Post

                                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.

                                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.