Mutex: Difference between revisions
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Puppydrum64 (talk | contribs) |
Puppydrum64 (talk | contribs) (→{{header|6502 Assembly}}: formatting for better readability) |
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main: |
main: |
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;if your time-sensitive function has parameters, pre-load them into global memory here. |
;if your time-sensitive function has parameters, pre-load them into global memory here. |
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;The only thing the NMI should have to do is write the data to the hardware registers. |
;The only thing the NMI should have to do is write the data to the hardware registers. |
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jsr waitframe |
jsr waitframe |
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LDA #$01 ;there's not enough time for a second vblank to occur between these two calls to waitframe(). |
LDA #$01 ;there's not enough time for a second vblank to occur between these two calls to waitframe(). |
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halt: |
halt: |
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jmp halt ;we're done - trap the cpu. NMI will still occur but nothing of interest happens since the mutex is locked. |
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jmp halt |
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; |
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nmi: ;every 1/60th of a second the CPU jumps here automatically. |
nmi: ;every 1/60th of a second the CPU jumps here automatically. |
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pha |
pha |
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LDA #$01 |
LDA #$01 |
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STA vblankflag ;allow waitframe() to exit |
STA vblankflag ;allow waitframe() to exit |
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pla |
pla |
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pla ;popAll |
pla ;popAll |
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rti |
rti |
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; |
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waitframe: |
waitframe: |
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pha |
pha |
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pla |
pla |
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rts</lang> |
rts</lang> |
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=={{header|8086 Assembly}}== |
=={{header|8086 Assembly}}== |
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<code>LOCK</code> is a prefix that can be added to instructions that read a value then write back to it, such as <code>INC</code> and <code>DEC</code>. This prefix "locks" the memory bus, preventing other CPUs (if any) from accessing the same memory location at the same time as the CPU executing the "locked" instruction. The lock lasts until the locked instruction is complete, at which point the lock is released. This isn't used much on the original 8086, and there are a few limitations to the usage of the <code>LOCK</code> prefix: |
<code>LOCK</code> is a prefix that can be added to instructions that read a value then write back to it, such as <code>INC</code> and <code>DEC</code>. This prefix "locks" the memory bus, preventing other CPUs (if any) from accessing the same memory location at the same time as the CPU executing the "locked" instruction. The lock lasts until the locked instruction is complete, at which point the lock is released. This isn't used much on the original 8086, and there are a few limitations to the usage of the <code>LOCK</code> prefix: |
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