Shifter Operations; Shifter Input/Output Registers - Analog Devices adsp-2100 Manual

2 Computational Units
2.4.2
The shifter performs the following functions (instruction mnemonics
shown in parentheses):
• Arithmetic Shift (ASHIFT)
• Logical Shift (LSHIFT)
• Normalize (NORM)
• Derive Exponent (EXP)
• Block Exponent Adjust (EXPADJ)
These basic shifter instructions can be used in a variety of ways,
depending on the underlying arithmetic requirements. The following
sections present single and multiple precision examples for these
functions:
• Derivation of a Block Exponent
• Immediate Shifts
• Denormalization
• Normalization
The shift functions (arithmetic shift, logical shift, and normalize) can be
optionally specified with [SR OR] and HI/LO modes to facilitate
multiprecision operations. [SR OR] logically ORs the shift result with the
current contents of SR. This option is used to join two 16-bit quantities into
a 32-bit value in SR. When [SR OR] is not used, the shift value is passed
through to SR directly. The HI and LO modifiers reference the shift to the
upper or lower half of the 32-bit SR register. These shift functions take
inputs from either the SI register or any other result register and load the
32-bit shifted result into the SR register.

2.4.2.1 Shifter Input/Output Registers

The sources of shifter input and output are:
Source for
Shifter input
SI
AR
MR0, MR1, MR2
SR0, SR1
2 – 28

Shifter Operations

Destination for
Shifter output
SR (SR0, SR1)