If the value of the pin STB (Strobe Input) falls to low level, then
Answer & step-by-step solution
In strobed input operation, a LOW pulse on STB̅ tells the 8255 that valid peripheral data is present and causes the input port data to be loaded into the input latch. The corresponding buffer-full/status logic is then updated.
Concept & Reasoning
STB̅ is an active-low peripheral handshake signal in Mode 1 input. Its falling/low action captures input data so the CPU can later read a stable latched value. Output latches are associated with output-mode handshake signals such as OBF̅, not with the STB̅ input event.
How to Solve It in the Exam
STB = strobe input → input latch.
Important Exam Point
Active-low notation means LOW is the asserted condition.
Quick Trick
STB = strobe input → input latch.
Common Mistake
Loading the output latch when an input strobe is received.
यदि STB (Strobe Input) पिन का मान निम्न स्तर पर गिरता है, तो
उत्तर और चरणबद्ध हल
A — इनपुट पोर्ट इनपुट लैच में लोड होता है। स्ट्रोब्ड इनपुट में STB̅ पर LOW पल्स 8255 को बताती है कि पेरिफेरल डेटा वैध है, और इनपुट पोर्ट डेटा इनपुट लैच में लोड हो जाता है; फिर IBF स्टेटस अपडेट होता है।
विस्तृत हल (मूल भाषा में)
Concept & Reasoning
STB̅ is an active-low peripheral handshake signal in Mode 1 input. Its falling/low action captures input data so the CPU can later read a stable latched value. Output latches are associated with output-mode handshake signals such as OBF̅, not with the STB̅ input event.
How to Solve It in the Exam
STB = strobe input → input latch.
Important Exam Point
Active-low notation means LOW is the asserted condition.
Quick Trick
STB = strobe input → input latch.
Common Mistake
Loading the output latch when an input strobe is received.
જો STB (Strobe Input) પિનનું મૂલ્ય નીચા સ્તરે જાય, તો
જવાબ અને પગલાવાર ઉકેલ
A — ઇનપુટ પોર્ટ ઇનપુટ લેચમાં લોડ થાય છે. સ્ટ્રોબ્ડ ઇનપુટમાં STB̅ પર LOW પલ્સ 8255ને જણાવે છે કે પેરિફેરલ ડેટા માન્ય છે, અને ઇનપુટ પોર્ટ ડેટા ઇનપુટ લેચમાં લોડ થાય છે; પછી IBF સ્ટેટસ અપડેટ થાય છે.
વિગતવાર ઉકેલ (મૂળ ભાષામાં)
Concept & Reasoning
STB̅ is an active-low peripheral handshake signal in Mode 1 input. Its falling/low action captures input data so the CPU can later read a stable latched value. Output latches are associated with output-mode handshake signals such as OBF̅, not with the STB̅ input event.
How to Solve It in the Exam
STB = strobe input → input latch.
Important Exam Point
Active-low notation means LOW is the asserted condition.
Quick Trick
STB = strobe input → input latch.
Common Mistake
Loading the output latch when an input strobe is received.
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