ADVANCE MICROPROCESSOR AND MICROCONTROLLER

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ADVANCE MICROPROCESSOR AND MICROCONTROLLER UNIT
II
ELECTRONICS COMMUNICATION / ELECTRONICS
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SYLLABUS

• INTERFACING OF PERIPHERALS 8255
• INTERFACING OF PERIPHERALS 8253
• INTERFACING OF PERIPHERALS 8251
• SERIAL COMMUNICATION RS232

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OBJECTIVES
The course will provide knowledge to interface
peripherals with microprocessor-based systems.

• Examine the 8255
• Describe the function of the 8253/54 PIT
• Use of USART (Universal Synchronous /
  Asynchronous Receiver Transmitter) - 8251A
• Describes the RS232 standard

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INTERFACING OF PERIPHERALS 8255
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INTERFACING OF PERIPHERALS 8255

• The Intel 8255 Programmable  Peripheral
  Interface chip is a peripheral chip originally
  developed for the Intel 8085 microprocessor.
• Is a member of a large array of such chips, known
  as the MCS-85 Family. 

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PIN CONFIGURATION OF 8255
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Contd. PIN CONFIGURATION OF 8255

1. D0-D7 DATA BUS These are 8 bit bidirectional
   data bus lines. Connect to system data bus for
   data transfer between 8085 8255.
2. CS bar CHIP SELECT It is active low input
   signal. If CS bar0 then 8255 is in active state
   when CS bar1 then 8255 is in deactive state.
3. RD bar READ It is active low input signal used
   in coordination with other signals to send data
   to CPU through data lines.

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Contd. PIN CONFIGURATION OF 8255
4. WR bar WRITE it is active low input signal
used in coordination with other signal to write
data to 8255. 5. A0-A1 ADDRESS LINES these are
input, active high address lines used to
distinguish different parts of 8255.
A1 A0 Function
0 0 port A
0 1 port B
1 0 port C
1 1 control register
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Contd. PIN CONFIGURATION OF 8255

• RESET This is an active high input signal. When
  8255 is reset , it clear control word register
  all ports are set to input modes.
• PA0-PA7 PORT A PINS 0 TO 7 these are 8 bit
  bidirectional I/O pins used to read data from
  peripheral.

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Contd. PIN CONFIGURATION OF 8255

• PB0-PB7 PORT B PINS 0 TO 7 These are 8 bit
  bidirectional I/O pins used same as PA0-PA7.
• 9. PC0-PC7 PORTS C PINS 0 TO 7 These are
  bidirectional I/O pins.

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BLOCK DIAGRAM OF 8255
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CONTD. BLOCK DIAGRAM OF 8255

• The 8255 has 24 input/output pins in all.
• Divided into three 8-bit ports.
• Port A 8-bit input/output ports.
• Port B 8-bit input/output ports.
• Port C can be used as an 8-bit input/output port

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Features of 8255

• It is programmable, parallel I/O device.
• It contains 24 programmable I/O pins.
• Fully compatible with Intel microprocessor
  families.
• Direct bit set/reset capability is available for
  port c.
• Improve DC driving capability.
• It can operate in 3 modes
• Mode 0 simple I/O
• Mode 1 strobed I/O
• Mode 2 strobed bidirectional I/O
  
  
  
  
  
  

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INTERFACING OF PERIPHERALS 8253
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8253 PROGRAMMABLE INTERVAL COUNTER

• There are 3 counter in this.
• The input frequency can be divided from
  1,2,-----,65536.
• Input clk frequency is 0 to 2 MHz.
• Shape of the output frequency
• 1.square wave
• 2. 1-shot
  
• 3.square wave with various duty cycles

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Contd... 8253 PROGRAMMABLE INTERVAL COUNTER

• Gate is used to enable or disable the counter.
• Bidirectional data bus D0-D7 is connected to the
  D0-D7 of the system bus.

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PIN DIAGRAM OF 8253
D7
VCC
D6
WR
D5
RD
D4
CS
D3
A1
8253
D2
A0
CLK 2
D1
OUT 2
D0
CLK 0
GATE 2
OUT 0
CLK 1
GATE 0
OUT 1
GND
GATE 2
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ARCHITECTURE OF 8253
CLK 0
DATA BUS BUFFER
COUNTER 0
GATE 0
D7-D0
OUT 0
RD WR A0 A1
CLK 1
READ/ WRITE LOGIC
COUNTER 1
GATE 1
OUT 1
CS
CLK 2
CONTROL WORD REGISTER
COUNTER 2
GATE 2
OUT 2
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CONTROL WORD REGISTER (CWR)
SC1 SC0 RL1 RL0 M3 M1 M0 BCD
D7 D6 D5 D4 D3
D2 D1 D0
D0 bit 0 Binary counter 1 BCD
counter
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D1-D2-D3 bit
M2 M1 M0 MODE
0 0 0 MODE 0
0 0 1 MODE 1
X 1 0 MODE 2
X 1 1 MODE 3
1 0 0 MODE 4
1 0 1 MODE5
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D4-D5 bit
RL1 RL0 FUNCTION
0 0 Counter latching
0 1 Read/ write LSB
1 0 Read/write MSB
1 1 Read/write LSB then MSB
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D6-D7 bit
D6 D7 COUNTER
0 0 COUNTER 0
0 1 COUNTER 1
1 0 COUNTER 2
1 1 ILLEGAL
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MODES OF 8253
MODE 0 Interrupt on terminal count. MODE 1
Programmable 1 shot. MODE 2 Rate
generator. MODE 3 Square wave generator. MODE
4 Software triggered strobe. MODE 5 Hardware
triggered strobe.
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INTERFACING OF PERIPHERALS 8251
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INTERFACING OF PERIPHERALS 8251

• Intel 8251A is a universal synchronous
  asynchronous Receiver Transmitter compatible
  with Intel's processor.

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INTERNAL ARCHITECTURE OF PERIPHERAL 8251 A
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BLOCK DESCRIPTION

• DATA BUS BUFFER INTERVAL BUS OF THE
  CIRCUIT WITH THE SYSTEM BUS
• READ/WRITE CONTROL CONTROLS THE OPERATION OF
  PERIPHERAL DEPENDING UPON THE OPERATION INITIATED
  BY THE CPU

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Contd. BLOCK DESCRIPTION

• MODEM CONTROL HANDLES THE MODEM HANDSHAKE
  SIGNALS TO COORDINATE THE COMMUNICATION BETWEEN
  THE MODEM THE USART

• TRANSMIT CONTROL TRANSMITS THE DATA BYTE
  RECEIVED BY THE DATA BUFFER FROM THE CPU FOR
  FURTHER SERIAL COMMUNICATION

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Contd. BLOCK DESCRIPTION

• TRANSMIT BUFFER PARALLEL TO SERIAL CONVERTER
  THATRECEIVE A PARALLEL BYTE FOR CONVERSION INTO
  A SERIAL SIGNAL

• RECEIVE CONTROL DECIDES THE RECEIVER FREQUENCY
  AS CONTROLLED BY THE RXC INPUT FREQUENCY

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PIN DIAGRAM OF 8251
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SERIAL COMMUNICATION RS232
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SERIAL COMMUNICATION RS232

• The RS232 interface is a standard interface
  developed by the Electronics Industries
  Association(EIA).
• Communication as defined in the RS232 standard is
  an asynchronous serial communication method.

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ContdSERIAL COMMUNICATION RS232

• The word Serial means that the information is
  sent one bit at a time. Asynchronous tells us
  that the information is not sent in predefined
  time slots. Data transfer can start at any given
  time and it is the task of the receiver to detect
  when a message starts and ends.
• RS232 (Recommended Standard 232) is a standard
  for serial binary data signals connecting between
  a DTE and a DCE. It is commonly used in computer
  serial ports.

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ContdSERIAL COMMUNICATION RS232

• The standard has been renamed as the sponsoring
  organization changed its name, and has been
  variously known as EIA RS232, EIA 232 and most
  recently as TIA 232.
• The current version is TIA-232-F Interface
  Between Data Terminal Equipment and Data
  Circuit-Terminating Equipment Employing Serial
  Binary Data Interchange, issued in 1997.

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ContdSERIAL COMMUNICATION RS232

• RS-232 has been around as a standard for
  decades as an electrical interface between Data
  Terminal Equipment (DTE) and Data
  Circuit-Terminating Equipment (DCE) such as
  modems.

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RS-232 DB9 Pin Out
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RS-232 DB25 Pin Out
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Signal Description

• TxD This pin carries data from the computer to
  the serial device
• RxD This pin carries data from the serial device
  to the computer
• DTR signals DTR is used by the computer to
  signal that it is ready to communicate with the
  serial device like modem. In other words, DTR
  indicates to the Dataset (i.e., the modem or
  DSU/CSU) that the DTE (computer) is ON.

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Signal Description Contd.

• DSR Similarly to DTR, Data set ready (DSR) is an
  indication from the Dataset that it is ON.
• DCD Data Carrier Detect (DCD) indicates that
  carrier for the transmit data is ON.
• RTS This pin is used to request clearance to
  send data to a modem.

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Signal Description

• CTS This pin is used by the serial device to
  acknowledge the computer's RTS Signal. In most
  situations, RTS and CTS are constantly on
  throughout the communication session.
• Clock signals (TC, RC, and XTC) The clock
  signals are only used for synchronous
  communications. The modem or DSU extracts the
  clock from the data stream and provides a steady
  clock signal to the DTE. Note that the transmit
  and receive clock signals do not have to be the
  same, or even at the same baud rate.

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Contd. Signal Description

• CD CD stands for Carrier Detect. Carrier Detect
  is used by a modem to signal that it has a made a
  connection with another modem, or has detected a
  carrier tone. In other words, this is used by the
  modem to signal that a carrier signal has been
  received from a remote modem.

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Contd. Signal Description

• RI RI stands for Ring Indicator. A modem
  toggles(keystroke) the state of this line when an
  incoming call rings your phone. In other words,
  this is used by an auto answer modem to signal
  the receipt of a telephone ring signal.
• The Carrier Detect (CD) and the Ring Indicator
  (RI) lines are only available in connections to a
  modem. Because most modems transmit status
  information to a PC when either a carrier signal
  is detected (i.e. when a connection is made to
  another modem) or when the line is ringing, these
  two lines are rarely used.

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Signal Description
Signal Signal Signal Origin Origin DB-25 pin
Name Typical purpose Abbreviation DTE DCE DB-25 pin
Data Terminal Ready Indicates presence of DTE to DCE. DTR ? 20
Data Carrier Detect DCE is connected to the telephone line. DCD ? 8
Data Set Ready DCE is ready to receive commands or data. DSR ? 6
Ring Indicator DCE has detected an incoming ring signal on the telephone line. RI ? 22
Request To Send DTE requests the DCE prepare to receive data. RTS ? 4
Clear To Send Indicates DCE is ready to accept data. CTS ? 5
Transmitted Data Carries data from DTE to DCE. TxD ? 2
Received Data Carries data from DCE to DTE. RxD ? 3
Common Ground GND common common 7
Protective Ground PG common common 1
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Specifications of RS232
Sr. No. Specifications RS232
1. Mode of Operation Single-Ended
2. Allowed no. of Tx and Rx 1 Tx, 1 Rx
3. Maximum cable length 50 Feet
4. Maximum data rate 20 kbps
5. Minimum driver output range 5V to 15V
6. Maximum driver output range 25V
7. Tx load impedance (Ohms) 3k to 7k
8. Rx input sensitivity 3V
9. Rx input voltage range 15V
10. Maximum Rx input resistance (Ohms) 3k to 7k
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Summary

• 8255 It has 24 input/output lines which may be
  individually programmed in two groups of twelve
  lines each, or three groups of eight lines.
• 8253 Its function is that of a general purpose,
  multi-timing element that can be treated as an
  array of I/O ports in the system software.
• The 8251 receives parallel data from the CPU and
  transmits serial data after conversion.
• Serial Communication RS232

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REFERENCES

• Advanced Microprocessors and Peripherals by
  A.K.Ray K.M.Bhurchandi
• www-ec.njit.edu/khader/classes/cet410/
• Chapter2011.ppt
• www-ec.njit.edu/khader/classes/ecet410/
• Chapter2003.ppt
• www.sparkfun.com/datasheets/Components/DS1307.pdf