iComp A1200 RTC Module co-exist with Accelerator RTC ?

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Don't Panic. Please wash hands.
  • Hello,


    I have a generic Amiga RTC question. It's more about the Amiga's architecture and how it interacts with RTC units (either plugged in the A1200's clockport or those found on all kinds of accelerator boards).


    I purchased an accelerator board without a battery. It had leak-damage and the previous owner removed it. The RTC chip (OKI M6242B) works fine but there is trace-damage between the battery and the RTC chip so the RTC is not powered while the Amiga 1200 is powered off. I hence need to enter the date and time at each power-on and this is annoying.


    So far, I can't find anyone that can fix the Circuit board and re-establish contact between the new battery and the board's RTC because no one has the technical information about this accelerator. The battery is a "Panasonic VL1220 HFN 3V 7mAh" which I soldered on myself and which is used often on such boards.


    I like Jens his products (I have the AGA Mk3 and it's great) and trust his RTC Module will work fine too. So could I buy the iComp A1200 RTC Module and have it's RTC with onboard CR1220 Battery be used as the only RTC or will it conflict with the accelerators onboard RTC which is, after all, still alive.


    Kind regards,

    Steve

  • I hence need to enter the date and time at each power-on and this is annoying.

    Do you have network in that computer? There's an NTP client for the Amiga (see Aminet) that can spare you the work.


    So could I buy the iComp A1200 RTC Module and have it's RTC with onboard CR1220 Battery be used as the only RTC or will it conflict with the accelerators onboard RTC which is, after all, still alive.

    The RTC module will use the exact same signals as the accelerator's RTC, so they will conflict. If you want the RTC module to work properly, you need to remove the Oki chip from the accel.

  • Hmmm I did not think about completely removing the RTC chip (and battery) from the board to be honest. Will it cause problems or have no effect at all?
    The board is an Apollo 1240 by the way. I'm very happy with it (I'm not supposed to say that out loud here :evil: )

    If it has no side-effects at all, i'll simply plug a battery-backed RTC unit in the motherboard's clock-port and problem solved.

  • Removing the RTC chip will have no effects on the accelerator part. There is no connection between the RTC chip and the rest of the board, apart from power connection.


    If you're not comfortable unsoldering the chip, you could raise the "select" pin from the board and tie it to VCC; this will "silence" the chip on the bus and make the RTC module work.


    The one thing you should not do is to connect the unmodified accelerator and the RTC module at the same time. This will cause bus contention where one of the RTC chips may fail permanently.

  • Yeah I figured having two (RTC) captains on one boat would spell disaster. So off with the board's RTC first (I'll simply desolder it) before your RTC solution is plugged in.

    I'll use Amiga Test Kit to make sure the RTC is not seen before going the next step.


    I have no idea which of the 18 pins the "select pin" is on this chip (I have the pinout but I'm a noob). With VCC you probably mean pin 18 on this chip? (pin 18 is labelled "VDD" (positive supply voltage).


    Link to pin-layout: https://www.amigawiki.org/doku.php?id=de:parts:m6242b

    (the RTC chip on my Apollo 1240 is an "OKI MSM6242B" which is a 18-pin DIP)

  • The "easy way" would be to lift pin#2, then make a connection with a 10k ohms resistor between pin#18 and that lifted pin. This will silence the chip.

  • Ok somebody shoot me. Could not lift pin 2 as those pins are super close to the SIMM slot and each other. I don't have the skills to pull that off. So I pulled something else off: the entire chip.

    All fine. System runs stable but has no RTC anymore. All good.


    Then I unpacked your package that came in the mail, happy to see the RTC module. Opened my A1200 and started crying ;( Turns out, I have a 1D4 motherboard with the clock-port pins on the "other" side...

    Found this image: https://bigbookofamigahardware…4_clockport_darkgreen.jpg
    On that same page, there is also an image of a 1D4 with the clock-port closer to the edge allowing the install of your RTC module.


    So I can't use this RTC module. The Module from AmigaKit is the same shape so won't work either. I must now find one that works with my version of the 1D4 board. No luck so far.


    Cannot use this module from Amigastore.eu either as my Indivision AGA MK3 is in the way.

    https://amigastore.eu/en/744-a…al-time-clock-module.html


    Man I need a drink... X/

  • So I can't use this RTC module. The Module from AmigaKit is the same shape so won't work either. I must now find one that works with my version of the 1D4 board. No luck so far.

    You won't find any RTC module that will work on that header, as it's plain in the wrong position. What you need to do to that board is to solder in the rest of the pins (18 pins) and plug the RTC module on the combined 18-pins-new and 4-pins of the old header, then the RTC module will work.

  • The last reply was more than 365 days ago, this thread is most likely obsolete. It is recommended to create a new thread instead.