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= MICROCODE OVERVIEW =

The DUO Compact's control unit contains 2 microcode EEPROM chips. The microcode determines the order in which to send read and write signals among other things. See the schematic for how the pins of the EEPROMs are connected.

= MICROCODE FORMAT =

Y = detect zero input (0 means zero NOT detected, 1 means zero detected)
Z = microcode address
X = unused pin
A = general address
B = general OE
C = ALU buffer OE
D = suffix selector (0 means use address register, 1 means use microcode value)
E = memory OE
F = reset clock counter (1 means reset)
P = memory WE (0 means write)
Q = general WE (0 means write)
R = data WE (1 means write)
S = address WE (1 means write)

The data AAABCDEX is contained in the first EEPROM, while XPQRSSTT is in the second EEPROM.
All OE pins are activated with an input of 0.

= MICROCODE DATA =

Write from memory (suffix 0) to general register 0


Write from memory (suffix 1) to general register 1


Write from memory (suffix 2) to general register 2


Write from memory (suffix 3) to general register 3


Write from memory (suffix 4) to general register 4


Write from memory (suffix 5) to general register 5


Write from memory (suffix 6) to general register 6


Write from memory (suffix 7) to general register 7


Write from general register 0 to address register 0


Write from general register 1 to address register 1


Write from memory to data register 0


Write from general register 2 to address register 0


Write from general register 3 to address register 1


Write from memory to data register 1


Write from ALU to memory


Write from general register 4 (or 6) to address register 0


Write from general register 5 (or 7) to address register 1


Go back to the first microcode step

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