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--- en:multiasm:exercisesbook:avr:sut [2026/04/30 10:46] – [Handling of the buffered 4-digit, 7-segment display] pczekalski
+++ en:multiasm:exercisesbook:avr:sut [2026/05/04 14:50] (current) – [Visualising Instruction Execution Time Using an Oscilloscope] pczekalski
@@ Line 340: / Line 340: @@
 <note tip>Nodes are interconnected in pairs: 1-2, 3-4, 5-6, 7-8, 9-10. Scenarios for data transmission between MCUs require booking and the use of correct nodes for sending and receiving messages.</note>
+==== Visualising Instruction Execution Time Using an Oscilloscope ====
+Let's try to visualise how code operates the GPIO. Naturally, in the remote lab, it is not possible to do it remotely, so here we present some desk-based experiments.\\
+The ''LAT_PIN'' is GPIO4, and an oscilloscope is connected to it.
+In the function that displays a single digit, there is a section that loads a binary mask into the internal registers, enabling the LED segments that constitute the digit to be turned on and off. It is:
+<code asm>
+...
+    sbi LAT_PORT, LAT_PIN
+    cbi LAT_PORT, LAT_PIN
+...
+</code>
+The figures {{ref>arduinounodigitoscilloscope1}} and {{ref>arduinounodigitoscilloscope2}} present the ''LAT_PIN'' signal, called periodically during the display of the consecutive digits (they represent the same signal but differ by the oscilloscope time base for better observation).\\
+''SBI'' causes the signal to rise, while ''CBI'' to fall. Thus, the HIGH time is the exact time during which the CBI instruction executes. It takes about 120-130ns.\\
+The Arduino Uno operates at 16 MHz, so each cycle is 1/16000000 s, which is about 63 ns. According to the documentation, ''CBI'' takes 2 cycles, which is ~126ns.
+<figure arduinounodigitoscilloscope1>
+{{:en:multiasm:exercisesbook:avr:pic_1054.png?300|}}
+<caption>''LAT_PIN'' signal (50ns time base)</caption>
+</figure>
+<figure arduinounodigitoscilloscope2>
+{{:en:multiasm:exercisesbook:avr:pic_1055.png?300|}}
+<caption>''LAT_PIN'' signal (25ns time base)</caption>
+</figure>

en/multiasm/exercisesbook/avr/sut.1777535207.txt.gz · Last modified: 2026/04/30 10:46 by pczekalski