The 8 bit control unit.
Notes
- Review the microcode for the 8-bit computer
- Ben builds a microcontroller
- This has a μpc - from a counter (74x161)
- An eeprom containing the microcode (two 28c16 chips)
- The &mupc; steps each clock cycle
- Each clock cycle, a μinstruction is fetched from the eeprom
- The address of the μinstruction is
- The op-code for the instruction to be executed (in ir 4-7)
- The μpc (3 bits).
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- The bits of the microinstruction power the individual lines to the different functional units of the pc.
- The μinstruction:
- 7 bit address (ir[4..7],μpc)
- His code to write to the eeprom
- HLT MI RI RO IO II AI AO EO SU BI OI CE CO
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- His entire instruction code:
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- Note all instructions start with Fetch
- IR XXXX μpc 0000 : MI|CO
- IR XXXX μpc 0001 : RO|II|CE
HLT MI RI RO IO II AI AO EO SU BI OI CE CO 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 1 0 0 0 0 0 0 1 0
- This video shows doing this.
- Look at about 22:08 for the final functioning machine.
- Note the control word in the lower right hand corner.
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