Control Data Cyber 170 State Hardware Reference Manual page 33

Instruction Section
Shift Sequence
The s h i f t sequence c o n t r o l s i n s t r u c t i o n s t h a t r e q u i r e s h i f t i n g t h e 60-bit
f i e l d of d a t a w i t h i n t h e operand word. The s h i f t i n s t r u c t i o n s a r e :
20
Left s h i f t (Xi) by jk LXI jk
21 Right s h i f t ( x i ) by jk
AXi jk
22 Left s h i f t (Xk) nominally (Bj) places t o X i LXi Bj, Xk
23 Right s h i f t (Xk) nominalLy ( ~ j ) places t o X i AXI Bj, Xk
43 Form mask of jk b i t s t o X i M X i jk
The s h i f t sequence a l s o c o n t r o l s t h e pack and unpack i n s t r u c t i o n s .
I n t h e
packed f l o a t i n g format, t h e c o e f f i c i e n t i s contained i n . t h e lower 48 b i t s .
The s i g n and biased exponents a r e contained i n t h e upper 1 2 b i t s .
The unpack
i n s t r u c t i o n o b t a i n s the packed word from the Xk r e g i s t e r , d e l i v e r s the
c o e f f i c i e n t t o t h e X i r e g i s t e r , and d e l i v e r s the exponent t o t h e Bj r e g i s t e r .
The unpack and pack i n s t r u c t i o n s a r e :
26 Unpack (Xk) t o X i and Bj U X i Bj, X k
27 Pack (Xk) and (Bj) t o X i PXi Bj,
Xk
The s h i f t sequence a l s o c o n t r o l s t h e normalize operations.
The c o e f f i c i e n t
p o r t i o n of t h e operand i s r e p o s i t i o n e d , and the exponent i s a d j u s t e d so that
t h e most s i g n i f i c a n t b i t of t h e c o e f f i c i e n t i s i n t h e highest-order b i t
p o s i t i o n of t h e c o e f f i c i e n t , and t h e exponent i s decreased by t h e number of
b i t p o s i t i o n s s h i f t e d . The normalize i n s t r u c t i o n s are:
24
Normalize (Xk) t o X i and B j N X i Bj, X k
25 Round normalize (Xk) t o X i and Bj Z X i Bj,
Xk