ST20-C1 datasheet(142/205 Pages) STMICROELECTRONICS

142 / 205 page

142/205

signal

Code: 23 F5

Description: Perform the first par t of a semaphore signal (or V) on the semaphore

pointed to by Areg. If no process is waiting then the unsigned count is incremented. If

processes are waiting then the first process is removed from the queue and its

identifier placed in Breg ready to be run. The instruction returns a boolean value in

Areg stating whether a run process is required.

This instruction should be used in the following sequence:

ld semptr; signal; cj

continue; run; continue:

Definition:

if (frontptr

= NotProcess)

-- queue empty

{

word

′[Areg @ s.Count] ← word[Areg @ s.Count] + 1

Areg

′← false

Breg

′← undefined

}

else

-- queue not empty

{

if (frontptr = backptr)

-- one process on queue

word

′[Areg @ s.Front] ← NotProcess

else

-- many processes on queue

word

′[Areg @ s.Front] ← word[ frontptr @ pw.Link ]

Areg

′← true

Breg

′← frontptr

}

Creg

′← undefined

where frontptr = word[Areg @ s.Front]

backptr = word[Areg @ s.Back]

Status Register:

No effect

Comments:

Secondar y instruction.

The increment of the count is unchecked.

This instruction may require 4 accesses to memory. The semaphore structure

should be placed in on-chip memory if interrupt latency is critical.

ST20-C1 데이터시트(PDF) 142 Page - STMicroelectronics

ST20-C1 데이터시트(HTML) 142 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

데이터시트 다운로드

링크 URL