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MicroBlaze Processor Reference Guide
UG081 (v14.7)
Chapter 5:
MicroBlaze Instruction Set Architecture
imm
Immediate
Description
The instruction imm loads the IMM value into a temporary register. It also locks this value so it can
be used by the following instruction and form a 32-bit immediate value.
The instruction imm is used in conjunction with Type B instructions. Since Type B instructions have
only a 16-bit immediate value field, a 32-bit immediate value cannot be used directly. However, 32-
bit immediate values can be used in MicroBlaze. By default, Type B Instructions will take the 16-bit
IMM field value and sign extend it to 32 bits to use as the immediate operand. This behavior can be
overridden by preceding the Type B instruction with an imm instruction. The imm instruction locks
the 16-bit IMM value temporarily for the next instruction. A Type B instruction that immediately
follows the imm instruction will then form a 32-bit immediate value from the 16-bit IMM value of
the imm instruction (upper 16 bits) and its own 16-bit immediate value field (lower 16 bits). If no
Type B instruction follows the imm instruction, the locked value gets unlocked and becomes
useless.
Latency
•
1 cycle
Notes
The imm instruction and the Type B instruction following it are atomic; consequently, no interrupts
are allowed between them.
The assembler provided by Xilinx automatically detects the need for imm instructions. When a 32-
bit IMM value is specified in a Type B instruction, the assembler converts the IMM value to a 16-
bit one to assemble the instruction and inserts an imm instruction before it in the executable file.
imm
IMM
1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0
IMM
0
6
1
1
1
6
3
1
