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 The Motorola 68hc11
  • The goal is to follow the building of the motherboard of our robot which will be based on a Motorola micro-controller.
  • We made the choice of the micro-controller after a compromise between the number of Input/Output, the feature, the price, the available development tools and our needs.
The circuit can be easily found in the stores.
It costs less than 100 FF (~ $16) for A1 and F1 versions, and 150 FF (~ $25) for the E2 version
We try to build a card for a cost of about 200 FF (~ $33).
Programmatically speaking, we can find a freeware assembler from Motorola with a functions library available on the Motorola server assembler.
We can also use a C compiler : icc11. The main inconvenient of this compiler is that it does not support floating point numbers management. icc11
Finally a program that allows to transfer the code in .S19 format pcbug11



 µc features
  • Works up to 8 Mhz . Each clock cycle spends 4 cycle ticks.
  • Voltage : 5V
  • Number of instructions > 100
  • 512o of EEPROM memory for the program
  • 256 bytes of RAM
  • 1 16 bit counter/timer
  • 1 Watch dog , 1 RTI
  • 16 Input/Output that we can configure separately
  • 1 SCI, 1 SPI
  • SLEEP mode, bootstrap, extended, autonomous
  • 8 A/D converters
  • 52 pins PLCC box
  • On the upper-left part we can find a plane that allows to locate the pin 1
  • 68HC11


     Schema of the working board
    This board contains several components. For example, the quartz is required to let the board work correctly.
  • A 68HC11 A1 micro-controller is used.
  • 32 Ko of memory for programming (that is enough for this type of application). The micro-controller is able to address up to 64 Kb. [6811]
  • A 74hc138 address coding circuit, to manage external peripherals [74hc138]
  • A 74hc373 latch circuit, because the data and addresses bus is multiplexed.
  • A INTEL 8255 family IO circuit. [8255 (soon)]
  • A circuit for RS232 interface. [MAX232]
  • A NAND circuit for logical functions.[74hc00]
  • The following schemas show how the board is cabled.

    Carte 6811 non routée


    We can find there the whole components connected to the µC bus.

    The following picture shows the map of the board when routed. Dimensions are 10cm*11cm :

    Carte 6811 routée


    To build the card, you'll need a double-sided plate. You don't need to have metallic holes.
    Several componants (pull-up resistances) ar 1206-format CMS (a little bigger than 805 ones)



  •  Components list
    Liste :
  • 1 68hc11A1
  • 1 52 pins PLCC support
  • 1 74hc138
  • 1 µpd43256B (32ko RAM from NEC, any other model can feet)
  • 1 ram support
  • 1 MAX232
  • 1 Intel 8255
  • 1 74hc00
  • 1 74hc373
  • 1 8Mhz quartz
  • 2 100µF/16V radial capacitors
  • 6 tantales 1µF capacities
  • 1 2*36 pins breakable bar for connectors
  • 1 1*36 pins breakable bar for connectors
  • 1 1A model 7805 (TO220 box)
  • 2 100nF plastic capacitors
  • 2 22pF ceramic capacitors
  • 1 résistance 10M ohms
  • 8 10k ohms CMS 1206 resistances
  • 5 4.7 ohms CMS 1206 resistances
  • 1 1k Ohms resistance
  • 6 plastic 10nF capacitors
  • 1 switch for the reset
  • 2 1N4007 diods.

  • Last update : 10/15/1999