CHAPTER 27 CPU INSTRUCTION SET DETAILS
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Table 27-1. CPU Instruction Operation Notations
Symbol
Meaning
<-
Assignment.
||
Bit string concatenation.
x
y
Replication of bit value xinto a y-bit string. xis always a single-bit value.
x
y:z
Selection of bits ythrough zof bit string x Little-endian bit notation is always used. If yis less
than z this expression is an empty (zero length) bit string.
2’s complement or floating-point addition.
+
-
2’s complement or floating-point subtraction.
*
2’s complement or floating-point multiplication.
div
2’s complement integer division.
mod
2’s complement modulo.
/
Floating-point division.
<
2’s complement less than comparison.
and
Bit-wise logical AND.
or
Bit-wise logical OR.
xor
Bit-wise logical XOR.
nor
Bit-wise logical NOR.
GPR [x
General-Register x The content of GPR [0] is always zero. Attempts to alter the content of
GPR [0] have no effect.
Coprocessor unit z general register x
CPR [z, x
CCR [z, x
Coprocessor unit z control register x
COC [z
Coprocessor unit zcondition signal.
BigEndianMem Big-endian mode as configured at reset (0 -> Little, 1 -> Big). Specifies the endianness of the
memory interface (see LoadMemory and StoreMemory), and the endianness of Kernel and
Supervisor mode execution.
However, this value is always 0 since the V
R
4102 supports the little endian order only.
ReverseEndian Signal to reverse the endianness of load and store instructions. This feature is available in
User mode only, and is effected by setting the RE bit of the Status register. Thus,
ReverseEndian may be computed as (SR
25
and User mode).
However, this value is always 0 since the V
R
4102 supports the little endian order only.
BigEndianCPU The endianness for load and store instructions (0 -> Little, 1 -> Big). In User mode, this
endianness may be reversed by setting SR
25
. Thus, BigEndianCPU may be computed as
BigEndianMem XOR ReverseEndian.
However, this value is always 0 since the V
R
4102 supports the little endian order only.
T + i
Indicates the time steps between operations. Each of the statements within a time step are
defined to be executed in sequential order (as modified by conditional and loop constructs).
Operations which are marked T + i are executed at instruction cycle irelative to the start of
execution of the instruction. Thus, an instruction which starts at time jexecutes operations
marked T + i:at time i + j The interpretation of the order of execution between two instructions
or two operations which execute at the same time should be pessimistic; the order is not
defined.