1. T F The LC-3 uses special input/output instructions to communicate with I/O d
ID: 3836388 • Letter: 1
Question
1. T F The LC-3 uses special input/output instructions to communicate with I/O devices.
2. T F In the LC-3, when a key on the keyboard is pressed, KBDR holds the 2's complement representation of that key.
3. T F The LC-3 has two device registers to handle input from the keyboard. The keyboard data register (KBDR) and the keyboard status register (KBSR).
4. If the keyboard hardware writes to KBDR without checking the ready bit of KBSR, the following can happen.
a. Everything will work correctly.
b. The program can miss reading characters that were typed.
c. The program will read the same key multiple times.
d. No characters will be entered.
5. The test for an interrupt signal is generally done in which phase of the instruction cycle?
a. DECODE
b. OPERAND EVALUATION
c. EXECUTE
d. STORE RESULT
6. In the LC-3, interrupt-driven I/O for the keyboard is accomplished by the logical _______ of the Interrupt Enable bit and the Ready bit.
Explanation / Answer
1. T F The LC-3 uses special input/output instructions to communicate with I/O devices.
True, it has special instruction
2. T F In the LC-3, when a key on the keyboard is pressed, KBDR holds the 2's complement representation of that key.
True
3. T F The LC-3 has two device registers to handle input from the keyboard. The keyboard data register (KBDR) and the keyboard status register (KBSR).
True, KDBR has last read charcter, KDSR is set when a new char is entered
4. If the keyboard hardware writes to KBDR without checking the ready bit of KBSR, the following can happen.
a. Everything will work correctly.
b. The program can miss reading characters that were typed.
c. The program will read the same key multiple times.
d. No characters will be entered.
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