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Re: 32kB x 8 bit static RAM expansion module for TI-74 BASICALC or TI-95 PROCALC

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On Friday, March 6, 2020 at 11:32:37 AM UTC-5, Lorenz Born wrote:
> On 2020-03-06 15:30, Tom Lake wrote:
> > On Thursday, March 5, 2020 at 1:53:43 PM UTC-5, Lorenz Born wrote:
> >> Dear all,
> >>
> >> I had the unique opportunity to buy a pocket TI-95 PROCALC calculator
> >> together with a Math Statistics, a Chemical Engineering library module,
> >> a PC-324 printer and a PC interface for around $40 here in Switzerland.
> >>
> >> Now I'm considering how the internal memory of only 8kByte could be
> >> expanded with a RAM memory module (RAM cartridge) with 32 kByte. In my
> >> opinion, this should work, since a ROM expansion (ROM cartridge) with a
> >> memory size of 32 kByte was also available for the TI-95 PROCALC calculator.
> >>
> >> What do you think about that? Has anyone worked with such a RAM
> >> extension before? Probably built by yourself. Of course, I would have to
> >> develop it first. I imagine using a SAMSUNG KM62256CLG-7L (see
> >> https://app.ultralibrarian.com/details/Samsung/KM62256CLG-7L?uid=93ce5ab184e94c09)
> >> 32k x 8 bit low power CMOS static RAM (70ns).
> >>
> >> Would anyone other than me be interested in such a 32 kByte RAM
> >> cartridge? Thanks in advance for any help or comments.
> >>
> >> Best regards,
> >> Lorenz
> >> -- 
> >> Lorenz Born
> >> lorenz<dot>born<at>gmail<dot>com
> >> The computer gets faster! --Moore--
> > 
> > I had a rare TI 32K cartridge. It was directly usable on the TI-74 but to use all 32K on the 95, you needed to do some manipulation:
> > 
> > To allow full access:
> > (numbers are in Hex)
> > 
> > Store 20 in BFFC
> > Store 7F in BFF4
> > 
> > Key-by-key method:
> > 
> > 1. Enter Hex Mode by pressing CONV, BAS (on function key), HEX (on function key)
> > 2. Enter System mode by pressing FUNC, SYS (on function key), YES (on function key)
> > 3.Type 2,0
> > 4. Press STB (on function key)
> > 5. Type 2nd, B (on HYP key), 2nd, F (on RCL key), 2nd, F (on RCL key), 2nd C (on INCR key)
> > 6. Type 7, 2nd F (on RCL key)
> > 7. Type 2nd B (on HYP key), 2nd F (on RCL key), 2nd F (on RCL key), 4
> > 
> > Now when you do a CAT of the file space on the cartridge, it will show 32752 bytes free. You can remove the cartridge, insert other cartridges,
> > even press reset or insert the 32K cart in another machine. The number of free bytes on that 32K cart will still be correct.
> > The number of free bytes is stored on the cartridge.
> > 
> Tom, thank you for the very detailed explanation! This is new and very 
> interesting for me. What else is saved in the last 16 bytes of the 
> cartridge port memory map? Do you possibly know more about this? And why 
> the two values #20 in BFFC and #7F in BFF4? Can these two hexadecimal 
> values be explained? At the moment I don't see any connection with the 
> memory size of 32768 bytes.
> -- 
> Lorenz Born, Switzerland
> "The computer gets faster!" -- Gordon E. Moore

7F20 hex is decimal 32544. That's the memory size of the 32K cartridge after some bytes (224 decimal bytes) are taken for housekeeping. Since this is an 8-bit machine, you have to enter the hex value in two parts - 20 which is the LSB (least significant byte) and 7F which is the MSB (most significant byte)

I don't have any other information about data in the cartridge port. Sorry!

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32kB x 8 bit static RAM expansion module for TI-74 BASICALC or TI-95 PROCALC Lorenz Born <lorenz.born@gmail.com> - 2020-03-05 19:53 +0100
  Re: 32kB x 8 bit static RAM expansion module for TI-74 BASICALC or TI-95 PROCALC Tom Lake <tlake@twcny.rr.com> - 2020-03-06 06:30 -0800
    Re: 32kB x 8 bit static RAM expansion module for TI-74 BASICALC or TI-95 PROCALC Lorenz Born <lorenz.born@gmail.com> - 2020-03-06 17:32 +0100
      Re: 32kB x 8 bit static RAM expansion module for TI-74 BASICALC or TI-95 PROCALC Tom Lake <tlake@twcny.rr.com> - 2020-03-06 13:38 -0800
        Re: 32kB x 8 bit static RAM expansion module for TI-74 BASICALC or TI-95 PROCALC Lorenz Born <lorenz.born@gmail.com> - 2020-03-07 11:03 +0100
          Re: 32kB x 8 bit static RAM expansion module for TI-74 BASICALC or TI-95 PROCALC Tom Lake <tlake@twcny.rr.com> - 2020-03-07 06:04 -0800

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