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Powertran Cortex

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    It works!!! .... well almost, colour/vertical sync are a bit out of sorts on the UHF adapter. I haven't tried component video out yet. but I think we have a test-bed machine. Ran a sample basic program, fine.

    Now to put a bit more floor down & earn some "ram testing" time.
    "Don't it always seem to go
    That you don't know what you’ve got ‘til it’s gone" (BANG )

    Comment


      Originally posted by nige the hippy View Post
      It works!!! .... well almost, colour/vertical sync are a bit out of sorts on the UHF adapter. I haven't tried component video out yet. but I think we have a test-bed machine. Ran a sample basic program, fine.

      Now to put a bit more floor down & earn some "ram testing" time.
      Great news! The vertical sync issue may be due to a TMS9928 being fitted instead of a TMS9929. The 9928 has NTSC video timing while the 9929 is PAL. I had an old Fergusson TX9 TV and there was a simple resistor change to get it to sync up to the 30 frames/second.

      Comment


        Stuart, I've had a quick check with the logic probe ( set to TTL/LS and PULSE ) and got the following results:
        IC47 - CS2 = High initially, High when RESET held in and pulses for short duration when RESET released - Pulsing stops when RUN led goes out.
        IC46 - CS2 = High initially, High when RESET held in and pulses for short duration when RESET released - Pulsing stops when RUN led goes out.
        IC45 - CS2 = High initially, High when RESET held in and pulses for LONGER duration when RESET released - Pulsing stops when RUN led goes out.

        ADDRESS LINES
        The address line results can be divided into groups:
        A1, A2, A3, A4, A6, A7
        Without touching the reset button these are continually pulsing.(high, low and pulse lit)
        With the reset button held in, these address lines are LOW and start pulsing when RESET is released and then remain pulsing.
        A0, A5
        Without touching the reset button these are showing LOW with the occasional pulse LED every 3- 4 seconds
        With the reset button held in, these address line are LOW and start pulsing (high, low and pulse lit) when RESET is released, but only for the length of time that the RUN led is lit, then they return to their normal state of LOW with the occasional pulse LED every 3- 4 seconds.
        The question is, have I got the correct settings on the logic probe ? ?

        Nige - Great news about your Cortex - I could always try punishing mine by cutting its mains lead off !!

        Comment


          Originally posted by tms9995 View Post
          Great news! The vertical sync issue may be due to a TMS9928 being fitted instead of a TMS9929. The 9928 has NTSC video timing while the 9929 is PAL. I had an old Fergusson TX9 TV and there was a simple resistor change to get it to sync up to the 30 frames/second.
          You know you might be right! my eyesight's gone terrible in the past 5 years or so! I'll take another look. If you're not right, That area of the motherboard is a little crustier than the rest.
          However I've a microvitec cub, and a commodore 1084 monitor, It should be a case of making up adapter leads.
          I can still try the other dram chips in to see if they're ok.
          "Don't it always seem to go
          That you don't know what you’ve got ‘til it’s gone" (BANG )

          Comment


            Originally posted by tms9995 View Post
            Great news! The vertical sync issue may be due to a TMS9928 being fitted instead of a TMS9929. The 9928 has NTSC video timing while the 9929 is PAL. I had an old Fergusson TX9 TV and there was a simple resistor change to get it to sync up to the 30 frames/second.
            There are also two mods in the area of the sync separator circuit shown on the latest circuit diagram. This might be to improve the vertical sync?

            Comment


              Andy.

              (Logic probe settings sound fine).

              The EPROM chip selects sound fine - so that is another area of the circuit that seems to be working OK.

              Looks like you probed the address lines on the RAMs (A0 - A7), rather than the EPROMs (A0 - A12)?

              Comment


                AAAAARRGGHH no component video out (in spite of the hole on the backplate) it looks like there were issues with the sync, as there are hand drawn mods on the circuit diagram. There's monochrome composite out from the chip, so all is not lost. but I think it's out with the 'scope tomorrow, and a good root around.

                p.s Don't answer this one, Andy's problems need the attention.... incidentally it couldn't be a damaged eprom socket could it?
                "Don't it always seem to go
                That you don't know what you’ve got ‘til it’s gone" (BANG )

                Comment


                  Sorry Stuart - It's just me being a plonker again.

                  The info I gave you was for the Eprom pins A0 - A7 but I didn't spot A8 - A12 on the other side.
                  I'll have to give you the next thrilling instalment for A8 - A12 tomorrow.

                  Are my results what you would expect for the first 8 address lines?

                  Comment


                    They sound sort of OK! The activity when you release the reset button is good, but I'm not sure where this pulsing every 3-4 seconds is coming from.

                    When you release the reset button, the EPROM data is copied to RAM, so you should see activity on all the EPROM address lines for that 1 second. When the buzzer starts, the processor goes into a tight 'loop of death', so I would expect some lines to be static high, some static low, and a few pulsing. Not sure where the 3-4 second pulses are coming from - the processor shouldn't even be responding to interrupts.

                    Comment


                      Originally posted by nige the hippy View Post
                      it couldn't be a damaged eprom socket could it?
                      It's a possibility. IC47 is working well enough to at least read the reset vector from, and IC45 is working well enough to at least read the first part of the boot code.

                      Andy, can you pop the probe round all the address pins on *all* the EPROMs and check you have activity when you pop the reset button? Also check the *CS1 pin on each EPROM - should be pulsing even after the buzzer starts (I think). The PD pin on each should be static low. Check the power supply pins.

                      Nige - what might be a good way to check the data pins? Power off then check the resistance between the data pins on adjacent sockets?

                      Comment


                        Originally posted by Stuart View Post
                        Nige - what might be a good way to check the data pins? Power off then check the resistance between the data pins on adjacent sockets?
                        Sounds like a great idea, do a 3 way (ICs 45-46, 45-47, 46-47) continuity check on every pin.
                        "Don't it always seem to go
                        That you don't know what you’ve got ‘til it’s gone" (BANG )

                        Comment


                          Stuart,
                          I've re-checked all the pins and listed the indications below. The random pulse I was seeing every 3-4 seconds on A0 + A5 seems to have disappeared - Maybe it was my probe randomly triggering. Also the data pulse on A11 seems slower or a different format to that seen on other address pins - If this means anything.

                          ADDRESS LINES
                          The address line results can be divided into groups:
                          A1, A2, A3, A4, A6, A7, A12
                          Without touching the reset button these are continually pulsing.(high, low and pulse lit)
                          With the reset button held in, these address lines are LOW and start pulsing when RESET is released and then remain pulsing.
                          A0, A5, A8, A9, A10, A11
                          Without touching the reset button these are showing LOW
                          With the reset button held in, these address line are LOW and start pulsing (high, low and pulse lit) when RESET is released, but only for the length of time that the RUN led is lit, then they return to their normal state of LOW. * (ON A11 THE DATA PULSE SEEMS TO BE SLOWER THAN THE OTHERS)

                          CS1 (x3) = Initially pulsing High / Low -- Reset button in = High --- Button released = Pulsing High / Low
                          CS2 / IC47 = High initially, High when RESET held in and pulses for short duration when RESET released - Pulsing stops when RUN led goes out.
                          CS2 / IC46 = High initially, High when RESET held in and pulses for short duration when RESET released - Pulsing stops when RUN led goes out.
                          CS2 / IC45 = High initially, High when RESET held in and pulses for LONGER duration when RESET released - Pulsing stops when RUN led goes out.

                          PD (x3) Continuous Low = Uneffected by reset
                          Voltage between pin 14 and pins 1/26/28 = 4.85v - All Eproms
                          Q1 to Q8 = Initially High -- Reset button in = High --- Button released = Pulsing High / Low for duration of RUN led then continually High.

                          I also had a quick check of :
                          Pins 11 to 18 of IC44 = Initially no indication on probe -- Reset button in = No indication -- When the Reset Button is released, these are active for duration of RUN led then back to no indication.
                          Pins 5,6,7,9,10,11,12,13 of all the RAM chips = Initially pulsing High / Low -- Reset button in = Low --- Button released = Pulsing High / Low (High LED brighter for duration of RUN led)

                          The continuity check between the Eprom pins was also all good.

                          Andy
                          Last edited by andyp; February 25, 2010, 09:49 AM. Reason: Missed something

                          Comment


                            Well you have seem to have activity on all the lines - nothing has failed to pull a line permanently high or low.

                            What I would suggest is that you now wait until Nige has laid a bit more flooring and has earnt (!) the time to test his spare set of RAMs and post these down to you. Try these with your Forth EPROMs. It is possible that Forth isn't working because you have a bad RAM chip, and Basic isn't working because of a dodgy EPROM checksum (I don't think the Basic code is actually reading anything from RAM up to the point where the buzzer starts, and so it wouldn't notice a bad RAM chip). Then perhaps your Basic EPROMs back to Nige to test in his Cortex. If your Basic EPROMs are proven good - then on to plan B - whatever that is!

                            Stuart.

                            Comment


                              OK Stuart, Sounds like a plan !
                              Once again, thanks for all your time and effort, I didn't have a clue what to check.

                              Nige, I appreciate you rushing around and getting your Cortex up and running, but remember there's no rush, I can wait as long as you want.
                              It sounds like you've already got a list of jobs as long as your arm !

                              Comment


                                I haven't plugged the scope in, but I thought "what the hell..." so I've pulled one of the DRAMs Lo & behold it just sits there being dead with the "Basic" light lit, and the "Run" light glowing dully (does that sound familiar?). I popped one of the replacement Drams in, and it fires up fine, so they work in the machine as a valid substitute.
                                I can't test drams on my eprom programmer (it only does static ram), and I'm unwilling to do a lot of dram swapping on my cortex, so I'll pop 9 chips in the post in the hope that at least 8 will work. You probably only need one, so that gives you a set of 8 chips that will probably work to put in something else.
                                I suggest you swap them in one at a time so you know which one is faulty.
                                Of course, it could be something else!

                                Edit:- Just popped them in the post, but they probably won't go till monday morning now (there used to be a sunday collection from the box opposite )
                                Last edited by nige the hippy; February 27, 2010, 11:11 AM.
                                "Don't it always seem to go
                                That you don't know what you’ve got ‘til it’s gone" (BANG )

                                Comment

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