Loading ...
Sorry, an error occurred while loading the content.

Re: [cosmacelf] Re: membership card

Expand Messages
  • Peter de Vroomen
    Here s another idea ... I don t know how easy it is to make a bit-banged RS-232 port. But you could instead make a bit-banged I2C bus and use an I2C eeprom.
    Message 1 of 116 , Feb 3, 2005
    • 0 Attachment
      Here's another idea

      > - RS-232 port (bit-banger using Q and EF4)

      I don't know how easy it is to make a bit-banged RS-232 port. But you could
      instead make a bit-banged I2C bus and use an I2C eeprom. Those are generally
      DIL8 chips and don't take up much space at all.

      You would then also already have the I2C bus to connect the Nokia display.

      How large would an I2C bootloader be? Could it be toggled in by hand in a
      short time? Then you could pre-load the eeprom with all sort of routines.
      You could then toggle in the bootloader which copies the eeprom to ram, and
      then you could boot from ram.

      The stacking-boards design sounds very nice, by the way. At those low
      frequencies I don't expect any real problems.

      PeterV
    • ajparent1
      ... Lee, they run the gamut from cmos parts in the few mils range to around 100ma for the older nmos designs. I have some Alliance CMOS parts pulled from a 486
      Message 116 of 116 , Feb 27, 2005
      • 0 Attachment
        --- In cosmacelf@yahoogroups.com, Lee Hart <leeahart@e...> wrote:
        > One more thought. Can someone who has any of the skinny-DIP 28-pin
        > thru-hole 32k RAMs actually plug one into a breadboard and see how much
        > power they really take? If we can find one that is reasonably
        > inexpensive and available, we could use it on the MEMBER card to save a
        > chip.

        Lee, they run the gamut from cmos parts in the few mils range to
        around 100ma for the older nmos designs. I have some Alliance CMOS
        parts pulled from a 486 cache and they run about 12ma when supporting
        a z80/4mhz. Their drain is cycle time dependent for the cmos. I've
        looked and the general xx256 parts are still fairly easy to find and
        cheap. Do watch for the parts that are semi-static where the address
        lines are latched by CE/. Their power drain is very low but CE/ must
        be asserted for every access.

        Allison
      Your message has been successfully submitted and would be delivered to recipients shortly.