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LDH(U) Load Halfword From Memory With a 5-Bit Unsigned Constant Offset or Register Offset
3-132 Instruction Set SPRU733
The addressing arithmetic that performs the additions and subtractions
defaults to linear mode. However, for A4−A7 and for B4−B7, the mode can be
changed to circular mode by writing the appropriate value to the AMR
(see section 2.7.3, page 2-10).
For LDH(U), the values are loaded into the 16 LSBs of dst. For LDH, the upper
16 bits of dst are sign-extended; for LDHU, the upper 16 bits of dst are zero-
filled. The s bit determines which file dst will be loaded into: s = 0 indicates dst
will be loaded in the A register file and s = 1 indicates dst will be loaded in the
B register file. The r bit should be cleared to 0.
Increments and decrements default to 1 and offsets default to 0 when no
bracketed register or constant is specified. Loads that do no modification to the
baseR can use the syntax *R. Square brackets, [ ], indicate that the ucst5 offset
is left-shifted by 1. Parentheses, ( ), can be used to set a nonscaled, constant
offset. You must type either brackets or parentheses around the specified
offset, if you use the optional offset parameter.
Halfword addresses must be aligned on halfword (LSB is 0) boundaries.
Execution if (cond) mem
→ dst
else nop
Pipeline
Stage
E1 E2 E3 E4 E5
Read baseR
offsetR
Written baseR dst
Unit in use
.D
Instruction Type Load
Delay Slots 4 for loaded value
0 for address modification from pre/post increment/decrement
For more information on delay slots for a load, see Chapter 4.
See Also LDB, LDW
Pipeline