Minitel 5

The Minitel was a french dumb terminal with an embedded modem which had its Golden Age before the rise of Internet. Typically cubic, with an included CRT screen and, more importantly, you could have one at home for cheap (the model 1 was “lent” for free), so, it was a huge success and a lot of people (including me) had their first experience “being online” playing with that thing. The Minitel 5 was a version really more rare to encounter. Flat, with an LCD screen and contained a rechargeable battery, this “laptop-style” terminal could be used in phone booths and cars.

I’ve got one, but it is very strangely crashing at the second key press. As there seems to be no documentation yet available for it, I made this git repository.

EPROM Dumps

There are two 27C256 EPROM on the Minitel 5 board.

The first is the main EPROM, in socket MN3, containing all the firmware as the 80C32 microcontroller is ROMless. Beware, as my Minitel 5 is crashing, this ROM may be corrupted. If somebody can dump their own device, it could be very interesting for me to compare.

Link to the first dump file

The second EPROM, in socket MN8, is connected to the character generation IC and contains solely the bitmap font. 485 ’16-bytes’ zones from 0x6000 to 0x7E5F, with only the first 10 bytes used in each block (the 6 extra are always 0x00), one byte for each line of each character, where each bit is a pixel. Everything before address 0x6000 and from 0x7E50 to the end is filled with 0xFF.

Minitel 5 character generator EPROM content

Link to the second dump file

Integrated circuits

  • MN1 MHS 80C32 (MCU)
  • MN2 MHS MBSR-2000F11-5 DECOPLAT-1
  • MN3 NEC D27C256AD-15 (main EPROM)
  • MN4 Sharp LH5164-10 (backup RAM)
  • MN5 ROM/RAM “dual-dual row” (empty socket)
  • MN6 OKI M6255 (dot matrix lcd controller)
  • MN7 MHS MBSM-2000F05-5 VIDEOPLAT-1)
  • MN8 NEC D27C256AD-15 (bitmap font EPROM)
  • MN9 Philips FCB61C65LL-70T (SRAM)
  • MN10 Philips FCB61C65LL-70T (SRAM)
  • MN11 Motorola HC245A (3–state octal latch)
  • MN12 Motorola HC245A (3–state octal latch)
  • MN13 Motorola HC00A (quad 2-input NAND gate)
  • MN14 Harris HC04 (hex inverter)
  • MN15 Motorola HC245A (3–state octal latch)
  • MN16 Motorola HC245A (3–state octal latch)
  • MN18 Motorola HC4075 (triple 3-input OR gate)
  • MN19 RCA(?) HC273 (octal D latch w/common clock and reset)
  • MN201 ST TSB7513CP (single chip asynchronous FSK modem)
  • MN202 Philips PC74HC4053T (triple 2-channel analog multiplexer/demultiplexer)
  • MN203 TI(?) 27M4C (quad low power CMOS op-amp)
  • MN204 ST EFG71891PD (DTMF generator w/serial input)
  • MN205 Harris HC4052 (dual 4-channel analog multiplexer/demultiplexer)
  • MA103 LM3578N (DIP-8 switching regulator)
  • MA104 ADC0831CCN (single differential input 8-bit ADC w/serial I/O)
  • MA105 LM385M (1.2V micropower voltage reference)
  • MA201, MA202, MA203 Harris H11AG2 (phototransistor optocouplers)

More to come!

I already have some schematics. But i’m already now fucking tired doing this! 😡

Acknowledgements

People I wish to thank:

  • Ghyom for giving me that ancient device
  • Furrtek for his help for recognising Harris old IC logo and the 27M4C op-amp
  • Fréderic from CEM de Ronchin for his help in desoldering MN8
  • nikiroo for his spellchecks.

GitHub

View Github