Spectravideo MKI, Сервисное – Техническое руководство

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AHD
LOGIC UNIT (ALU)
The
8-b i t a r i thme t i c. and l o g i c a l in s t r uct ion of the CPU are execu ted in the
ALU.
Int erna l ly t he ALU c ommun i c a t e s w i th the reg i s t e rs and the ex te rna l data
bus on the interna l data bus . The type o f funct ions per forme d by the ALU
inc l ude :
Add
Subtract
Log ic a l AND
Log i c a l OR
Logic a l Exc l u s ive OR
Compa re
Le f t or right sh i f ts or rot a t e s
(
a r i thme t ic and log i ca l
)
Increment
Decrement
S e t b i t
Re s e t b i t
Te st b i t
INSTRUCTION REGISTERS
AN D
CPU CONTROL
As each i n s t r uc t ion i s f etche d from memory , i t is p l a c e d in the ins t ruc t ion
reg i s t e r and decode d . The c on t r o l sect ions performs t h i s func t ion and t hen
gene rat es and supp l ie s a l l o f the cont rol s i gna l s nec e s sar
y
to rea d or wri t e
da ta f rom or t o t h e reg i s t e rs , c ont rol the ALU and p rovide a l l re quire d
exte rna l cont rol s igna l s .
4 . 6