Page 29 - PIC18F4550微處理機C語言設計實務

૵ሔଡ଼ΥႧԊձ C ႧԊ 1

const：

ίᜊᅰΤ၈ۃࠦᅺͪ constdԨٜટረʚ੬ᅰ࠽f߰ᜊᅰ܁ѓމ੬ᅰdۆڌͪϤᅰ
މʔ̙஗һҷdᇜᙇኜۆึਗ਼Ϥᜊᅰᓖ׳ί೻όাኳ᜗ٙЗໄʕdν؈ᇜᙇኜ೯ତϞ

ɛΆྡᜊһdึ೯̈ᙆѓৃࢹf
Էνj

const unsigned char Var1 = 123; // Var1 ܁ѓމ੬ᅰ 123
Var1 = 0; // Άྡᜊһ੬ᅰ Var1 ۆᇜᙇኜึ೯̈ᙆѓ

volatile：

ΪᏐᇜᙇኜत׌d߰ᜊᅰ܁ѓމϤdۆڌͪϤᜊᅰ࠽ᎇ̙ࣛঐ஗ҷᜊdϾ˲ᇜᙇ
ழ᜗߰ආБ௰Գʷࣛdɰʔึਗ਼ϤᜊᅰٙהϞਗЪ՟ऊfɓছԴ͜ volatile ڌͪމ೷᜗

մᗙٙᅲπኜ€Timer, UARTneא٫݊ᅲπኜึΪމ̮௅፩ɝϾҷᜊ€PORTe
א݊ίʕᓙՌό༁ࠦהԴٙ͜ᜊᅰeᒔ݊ʔซ஗௰Գʷࡌҷٙᜊᅰf

Էνj

static volatile unsigned char PORTA @ 0x05;

ڌͪ PORTA வࡈЗ׵ 0x05 Зѧٙᜊᅰd̙ঐᎇࣛΪމՉ˼Ϊ९ҷᜊՉʫ࢙fԷ
νᛘ՟ PORTA ٙ࠽ܝdટഹࠅԱኽ༈࠽̘ਂкᓙϾӔ֛ʱ҉ٙਗЪࣛdᇜᙇኜ੬ึ

މə௰Գʷdఱ̥ᛘɓϣ PORTA ܝdఱɓٜਂ৙ਸ਼кᓙdӚΎ̘ࠠᛘ PORTAdԴ੻
௘ɝೌᇊ৙ਸ਼f܁ѓމ volatile ࣛdᇜᙇኜʔึމəಯˇ೻όڗܓϾ޲̘ਂࠠልᛘ՟
PORTA ٙਗЪf

presistent：

߰ᜊᅰ܁ѓމϤdۆڌͪϤᜊᅰί MCU ක֐઼ਗࣛʫ࢙Ԩʔึ஗૶ৰdϾ˲Ϥ
ᜊᅰึၾՉ˼ᜊᅰπ׳ίʔΝٙাኳ᜗Зໄf

Էνj

persistent long reset_count;

ڌͪ reset_count வࡈᜊᅰԨʔึΪމ MCU ࠠอ઼ਗࣛϾ஗૶ৰމཧdה˸̙˸
ί೻όක֐ଢ଼̋ϤᜊᅰϾ੻ٝࠠอ઼ਗٙϣᅰf

19