Multiplicand Register (Xt); Available Operations For Shifting Values In The Accumulator - Texas Instruments TMS320C28x Reference Manual

CPU Registers
Table 2−2. Available Operations for Shifting Values in the Accumulator
2.2.2

Multiplicand Register (XT)

2-8
Register Shift Direction
ACC Left
Right
AH or AL Left
Right
The multiplicand register (XT register) is used primarily to store a 32-bit signed
integer value prior to a 32-bit multiply operation.
The lower 16-bit portion of the XT register is referred to as the TL register. This
register can be loaded with a signed 16-bit value that is automatically sign-ex-
tended to fill the 32-bit XT register.
The upper 16-bit portion of the XT register is referred to as the T register. The
T register is mainly used to store a 16-bit integer value prior to a 16-bit multiply
operation.
The T register is also used to specify the shift value for some shift operations.
In this case, only a portion of the T register is used, depending on the instruc-
tion.
For example:
ASR AX, T
ASRL ACC, T
For these operations, the most significant bits of T are ignored.
Shift Type
Logical
Rotation
Arithmetic
Logical
Rotation
Logical
Arithmetic
Logical
performs an arithmetic shift right
based on the four least significant bits
of T: T(3:0) = 0...15
performs an arithmetic shift right by
the five least significant bits of T:
T(4:0) 0...31
Instruction
LSL or LSLL
ROL
SFR with SXM = 1
or ASRL
SFR with SXM = 0
or LSRL
ROR
LSL
ASR
LSR