PERIPHERAL INTERFACING
1. What is the use of 8051 chip?
Intel’s
8251A is a universal synchronous asynchronous receiver and transmitter
compatible with Intel’s Processors. This may be programmed to operate in any of
the serial communication modes built into it. This chip converts the parallel
data into a serial stream of bits suitable for serial transmission. It is also
able to receive a serial stream of bits and converts it into parallel data
bytes to be read by a microprocessor.
2. What are the different types of methods used for
data transmission?
The data transmission between points involves unidirectional or
bi-directional transmission of meaningful digital data through a medium. There
are basically there modes of data transmission
ü Simplex
ü Duplex
ü Half
Duplex
In simplex mode, data is transmitted only in one direction over a single
communication channel. For example, a computer (CPU) may transmit data for a
CRT display unit in this mode.
In duplex mode, data may be transferred between two trans receivers in
both directions simultaneously.
In half duplex mode, on the other hand, data transmission may take place
in either direction, but at a time may be transmitted only in one direction.
For example, a computer may communication with a terminal in this mode. When
the terminal sends data (i.e. terminal is sender).The message is received by
the computer (i.e. computer is receiver). However, it is not possible to
transmit data from the computer to terminal and from terminal to the computer
simultaneously.
3. What is the various programmed data transfer
method?
ü Synchronous
data transfer
ü Asynchronous
data transfer
ü Interrupt
driven data transfer
4. What is synchronous data transfer?
It is a data method which is used when the I/O device and the
microprocessor match in speed. The transfer a data to or from the device, the
user program issues a suitable instruction addressing the device. The data
transfer is completed at the end of the execution of this instruction.
5. What is asynchronous data transfer?
It is a
data transfer method which is used when the speed of I/O device does not match
with the speed of the microprocessor. Asynchronous data transfer is also called
as Handshaking.
6. What are the functional types used in control
words of 8251a?
The
control words of 8251A are divided into two functional types
Mode
Instruction control word: - This defines the general operational
characteristics of 8251A. Command Instruction control word: - The command
instruction controls the actual operations of the selected format like enable
transmit/receiver, error reset and modem control.
7. What are the basic modes of operation of 8255?
There are
two basic modes of operation of 8255, viz.
ü I/O mode.
ü BSR mode
In I/O mode, the 8255 ports work as programmable I/O ports, while in BSR
mode only port C (PC0-PC7) can be used to set or reset its individual port
bits. Under the IO mode of operation, further there are three modes of
operation of 8255, So as to support different types of applications, viz. mode
0, mode 1, and mode 2.
Mode 0-
Basic I/O mode
Mode
1-Strobe I/O mode
Mode 2-
Strobe bi-direction I/O
8. Write the features of mode 0 in 8255?
ü Two 8-bit
ports (port A and port B) and two 4-bit ports (port C upper and lower) are
available. Thetwo 4-bit ports can be
combined used as a third8-bitport.
ü Any port
can be used as an input or output port.
ü Output
ports are latched. Input ports are not latched.
ü A maximum of
four ports are
available so that
overall 16 I/O
configurations are possible.
9. What are the features used mode 1 in 8255?
ü Two
groups A and group B are available for strobe data transfer.
ü Each
group contains one 8-bit data I/O port and one 4-bit control/data port.
ü The 8-bit
data port can be either used as input or output port. The inputs and outputs
both are latched.
ü Out of
8-bit port C, PC0-PC2 is used to generate control signals for port B and
PC3=PC5 are used to generate control signals for port A. The inputs PC6, PC7
may be used as independent data lines.
10.
What are
the signals used in input control signal and output control signals?
ü Input
control signals
STB (Strobe input) IBF
(Input buffer full) INTR (Interrupt request)
ü Output control signal
OBF (Output buffer full) ACK (Acknowledge input)
INTR
(Interrupt request)
11. What are the features used mode 2 in8255?
The
signals 8-bit port in group A is available.
üThe 8-bit
port is bi-directional and additionally a 5-bit control port is available.
üThree I/O
lines are available at port C, viz PC2-PC0.
üInputs
and output are both latched.
üThe 5-bit
control port C (PC3-PC7) is used for generating/accepting handshake Signals for
the 8-bit data transfer on port A.
12.
What are
the modes of operation used in 8253?
Each of
the three counters of 8253 can be operated in one of the following six modes of
operation.
ü Mode 0
(Interrupt on terminal count)
ü Mode 1
(Programmable monoshot)
ü Mode 2
(Rate generator)
ü Mode 3
(Square wave generator)
ü Mode 4
(Software triggered strobe)
ü Mode 5
(Hardware triggered strobe)
13.
What are
the different types of write operations used in 8253?
There are
two types write operation in 8253
ü Writing a
control word register
ü Writing a
count value into a count register
The
control word register accepts data from the data buffer and initialize
ü Initializing
the operating modes (mode 0- mode 4)
ü Selection
of counters (counter 0- counter 2)
ü Choose
binary /BCD counters.
ü Loading
of the counter registers.
The mode
control register is a write only register and the CPU cannot read its contents.
14. Give the different types of command words used
in 8259A
The
command words of 8259A are classified in two groups
ü Initialization
command words (ICWs)
ü Operation
command words (OCWs)
15.
Give the
operation modes of 8259A?
ü Fully
Nest Mode
ü End of
Interrupt
ü Automatic
Rotation
ü Automatic
EOI mode
ü Specific
Rotation
ü Special
Mask Mode
ü Edge and
level Triggered Mode
ü Reading
8259 Status
ü Poll
command
ü Special
Fully Nested Mode
ü Buffered
Mode
ü Cascade
Mode
16.
Define
scan counter?
The scan counter has two modes to scan the key matrix and refresh the
display. In the encoded mode, the counter provides binary count that is to be
externally decoded to provide the scan lines for keyboard and display. In the decoded
scan mode, the counter internally decodes the least significant 2 bit and
provides a decoded 1 out of 4 scan on SL3-SL 3. The keyboard and display both
are in the same mode at a time.
17. What is the output modes used in 8279?
8279
provides two output modes for selecting the display options.
ü Display
scan
ü In this
mode, 8279 provides 8 or 16 character- multiplexed displays those can be
organized as dual 4-bit or single 8-bit display units.
ü Display
Entry 8279 allows options for data entry on the displays. The display data is
entered for display from the right side or from the left side.
18.
What are
the modes used in keyboard modes?
ü Scanned
Keyboard mode with 2 Key Lockout
ü Scanned K
e y b o a r d w i t h N -Key Rollover.
ü Scanned
Keyboard Special Error Mode.
ü Scanned
Matrix Mode.
19.
What are
the modes used in display modes?
1. Left
Entry Mode
In the
left entry mode, the data is entered from the left side of the display unit.
2. Right
Entry Mode
In the
right entry mode, the first entry to be displayed is entered on the rightmost
display.
20. What is the use of modem control unit in 8251?
The modem control unit handles the modem handshake signals to coordinate
the communication between the modem and the USART.
21. List the operation modes of 8255?
a) I/O Mode
ü Mode 0-
Simple Input/Output.
ü Mode 1-
Strobe Input/Output (handshake mode)
ü Mode 2-
Strobe bi-directional mode b) Bit Set/Reset Mode.
22. What is a control word?
It is a
word stored in a register (control register) used to control the operation of a
program digital device.
23. What is the purpose of control word written to
control register in 8255?
The control words written to control register specify an I/O function
for each I/O port. The bit D7 of the control word determines either the I/O
functions of the BSR function.
24. What is the size of ports in 8255?
Port - A : 8- bits Port
- B : 8- bits
Port -CU : 4- bits Port
-CL : 4- bits
25. What is an USART?
USART stands for universal Synchronous / Asynchronous Receiver /
Transmitter. It is a programmable communication interface that can communicate
by using either synchronous or asynchronous serial data.
26. What is the use of 8251 chip?
8251 chip is mainly used as the asynchronous serial interface between
the processor and the external equipment.
27. The 8279 is a programmable -----------------
interface.
Keyboard/
Display
28.
List the
major components of the Keyboard/ Display interface.
ü Keyboard
section
ü Scan
section
ü Display
section
ü CPUinterface
section
29.
What is
Key bouncing?
Mechanical switch are used as keys in most of the keyboard. When a key
is pressed the contact bounce back and forth and settle down only after a small
time delay (about 20ms). Even though a key is actuated once, it will appear to
have been actuated several times. This problem is called Key Bouncing
30. What is TXD?
TXD-
Transmitter Data Output
This
output pin carries serial of the transmitted data bits along with other
information like start bit, stop bits and priority bit.
31. Define HRQ?
The hold
request output request the access of the system bus. In non- cascaded 8257
systems, this is connected with HOLD pin of CPU. In cascade mode, this pin of a
slave is connected with a DRQ input line of the master 8257, while that of the
master is connected with HOLD input of the CPU.
32. What is RXD?
RXD-
Receive Data Input
This
input pin of 8251A receives a composite stream of the data to be received by
8251A.
33. What are the internal devices of a typical DAC?
The
internal devices of a DAC are R/2R resistive network, an internal latch and
current to voltage converting amplifier.
34. What is setting or conversion time in DAC?
The time
taken by the DAC to convert a given digital data to corresponding analog signal
is called conversion time.
35. What are the different types of ADC?
The
different types of ADC are successive approximation ADC, counter type ADC,
flash type ADC, integrator converters and voltage to frequency converters
Related Topics
Privacy Policy, Terms and Conditions, DMCA Policy and Compliant
Copyright © 2018-2023 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.