The Intel 8253, 8254, and 8259 are timers whereas Intel 8250 is a UART that is commonly used.
77. Which company developed 16450 CHIP?
A. Philips
B. Intel
C. National semiconductor
D. IBM
Answer: C
The Intel 8250 is replaced by the 16450 and 16550 which are developed by the National Semiconductors. 16450 is a chip that can combine all the PC’s input-output devices into a single piece of silicon.
78. What does ADS indicate in 8250 UART?
A. address signal
B. address terminal signal
C. address strobe signal
D. address generating the signal
Answer: C
The ADS is address the strobe signal and is working as active low in 8250 UART. The ADS signal is used to latch the address and chip select signals while processor access.
79. Which of the following signals are active low in the 8250 UART?
A. BAUDOUT
B. DDIS
C. INTR
D. MR
Answer: A
The BAUDOUT signal is active low whereas DDIS, INTR, and MR are active high in the 8250 UART. BAUDOUT is the clock signal from the transmitter part of the UART. DDIS signal goes low when the CPU is reading data from the UART. INTR is the interrupt pin. MR is the master reset pin.
80. Which of the signal can control bus arbitration logic in 8250?
A. MR
B. DDIS
C. INTR
D. RCLK
Answer: B
DDIS signal goes low when the CPU is reading data from the UART and it also controls the bus arbitration logic.
81. Which of the following is used to reset the device in 8250?
A. MR
B. DDIS
C. INTR
D. RCLK
Answer: A
MR is the master reset pin that helps to reset the device and restore the internal registers.
82. Which provides an input clock for the receiver part of the UART 8250?
A. RD
B. RCLK
C. MR
D. DDIS
Answer: B
RCLK provides an input clock for the receiver part of the UART. RD is the read signal. MR is the master reset pin and DDIS is used to control bus arbitration logic.
83. Which of the following is a general-purpose I/O pin?
A. OUT1
B. RD
C. ADS
D. MR
Answer: A
There are two general purposes I/O pin OUT1 and OUT2. OUT1 is set by the programming bit 2 of the MCR to a ‘1’ whereas OUT2 is set by the programming bit 3 of the MCR to ‘1’. These are active low pins in 8250.
84. Which of the following indicates the type of access that the CPU needs to perform?
A. MR
B. RD
C. ADS
D. RCLK
Answer: B
RD and WR signals are indicating the type of access that the CPU needs to perform, that is, whether it is a read cycle or write cycle.
85. Which pins are used for additional DMA control?
A. RXRDY
B. RD
C. MR
D. INR
Answer: A
The RXRDY and TXRDY are two active-low pins that are used for additional DMA control. It can be used for DMA transfers to and from the read and write buffers.
86. Which of the following are not used within the IBM PC?
A. TXRDY
B. BAUDOUT
C. ADS
D. OUT2
Answer: A
The CPU is responsible for moving data to and from the UART in the IBM PC, therefore it does not have TXRDY and RXRDY pins which are used for DMA accessing.
87. Which pins are used to connect an external crystal?
A. INR
B. ADS
C. XIN
D. SIN
Answer: C
The XIN and XOUT pins are used to connect an external crystal. These pins can also connect to an external clock.
88. Which UART is used in MC680 by 0 design?
A. Intel 8250
B. 16450
C. 16550
D. MC68681
Answer: D
The MC68681 is a standard UART developed by Motorola. It has been used in many MC680 by 0 designs.
89. Which of the following have a large FIFO buffer?
A. 8253
B. 8250
C. 16550
D. 16450
Answer: C
The largest buffer of 16 bytes is available on 16550 UART which is used for high-speed data communications.
90. Which of the following has a quadruple buffered receiver and a double-buffered transmitter?
A. Intel 8250
B. 16450
C. 16550
D. MC68681
Answer: D
The MC68681 is a standard UART developed by Motorola. It possesses a quadruple buffered receiver and a double-buffered transmitter.
