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LDB(U) Load Byte From Memory With a 5-Bit Unsigned Constant Offset or Register Offset
3-124 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 LDB(U), the values are loaded into the 8 LSBs of dst. For LDB, the upper
24 bits of dst values are sign-extended; for LDBU, the upper 24 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 0. 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.
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 LDH, LDW
Pipeline