Altera Nios II User Manual page 232

8–52
flushda
Operation:
Assembler Syntax:
Example:
Description:
Usage:
Exceptions:
Instruction Type:
Instruction Fields:
31 30 29 28 27 26 25
A
Nios II Processor Reference Handbook
Flushes the data cache line currently caching address rA + σ (IMM16)
flushda IMM16(rA)
flushda -100(r6)
If the Nios II processor implements a direct mapped data cache, flushda writes the data cache
line that is mapped to the specified address back to memory if the line is dirty, and then clears
the data cache line. Unlike flushd, flushda writes the dirty data back to memory only when
the addressed data is currently in the cache. This process comprises the following steps:
Compute the effective address specified by the sum of rA and the signed 16-bit immediate
■
value.
Identify the data cache line associated with the computed effective address. Each data cache
■
effective address comprises a tag field and a line field. When identifying the line, flushda
uses both the tag field and the line field.
Compare the cache line tag with the effective address to determine if the addressed data is
■
currently cached. If the tag fields do not match, the effective address is not currently
cached, so the instruction does nothing.
If the data cache line is dirty and the tag fields match, write the dirty cache line back to
■
memory. A cache line is dirty when one or more words of the cache line have been modified
by the processor, but are not yet written to memory.
Clear the valid bit for the line.
■
If the Nios II processor core does not have a data cache, the flushda instruction performs no
operation.
Use flushda to write dirty lines back to memory only if the addressed memory location is
currently in the cache, and then flush the cache line. By contrast, refer to
cache line" on page 8–51, "initd initialize data cache line" on page
data cache address" on page 8–56
For more information on the Nios II data cache, refer to the
chapter of the Nios II Software Developer's Handbook.
Supervisor-only data address
Fast TLB miss (data)
Double TLB miss (data)
MPU region violation (data)
I
A = Register index of operand rA
IMM16 = 16-bit signed immediate value
24 23 22 21 20 19 18 17
0
for other cache-clearing options.
16 15 14 13 12 11 10 9
IMM16
Chapter 8: Instruction Set Reference
Instruction Set Reference
flush data cache address
"flushd flush data
8–55, and "initda initialize
Cache and Tightly Coupled Memory
8 7 6 5 4 3 2
0x1b
February 2014 Altera Corporation
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