PC Interfacing Lecture - 09-2013

7/24/2019 PC Interfacing Lecture - 09-2013

http://slidepdf.com/reader/full/pc-interfacing-lecture-09-2013 1/36

Copyright © 2010, Dr. Vo Tuong Quan

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COMMUNICATION INTERFACING LECTURE

CONTENTS

1.

Overview2. Programmable Peripheral Interface 8255

3. Serial Communication (RS232, RS485, RS422…)

4.

I2C Standard

5.

SPI Standard

6.

Some popular communication Cards: DAQ Card/Motion Control Card

(PCLab 818L, PCI 1784, PCI 1772, PCI8254…)

7.

Controller Area Network (CAN) standard

8.

Network Communication Standard (Another Subject) LAN – Internet

9.

USB Standard10.

Integrated Technique

11. Group projects (Similar to the Microcontroller subject)

EVALUATION METHOD

ELearning Based10% Listing (randomly)

30% Homework – Class Test

20% Teamwork – Team Projects (4 students/team) present in weeks 14

and 15

40% Final test




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OVERVIEW

COMMUNICATION PURPOSES

- Transmit or receive data between/ among many equipments

- The communication data can be:

+ Control signals

+ Data signals

+ Status signals

ALL IS ….

Give an examples!

COMMUNICATION TYPES

- Half duplex

- Full duplex

DEFINITIONS

- DTE (Data Terminal Equipment)

The source of data generation/ the receiving data equipment. Ex: PC, MCU,

PLC,…

- DCE (Data Communication Equipment)




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The intermediate equipment. Ex: Modem, Switch, Router,…




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PROGRAMMABLE PERIPHERAL INTERFACE

8255

SPECIFICATION

- PPI8255 is the programmable parallel communication IC to choose the

suitable operation mode.

- This IC includes 3 input/output 8 bits parallel port (PortA, PortB, PortC)

and these ports can be devided into two groups of 12 bits. Group1:

PortA and high nibble of PortC; Group2: PortB and low nibble of

PortC.- There operation modes: Mode0, Mode 1 and Mode 2.




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Function diagram

Data Bus Buffer

- Include 8 data lines, 3 status mode, 2 directions, connect directly to

system bus.

- The direction of data bus buffer is controlled by the Read/Write

Control Logic.

- Data bus buffer is the communication port between 8255 and CPU

(Central Processing Unit) or MCU (Micro Controller Unit) including

data and control word.

Read/Write Control Logic

- Receive control signals and address from system to control operation

mode of 8255.

- 0CS : 8255 run.

- RESET: Let the 8255 to the initial state.

- 01, A A : Choose the ports and control word of 8255.




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- WR RD, : input or output mode.

- The operation mode of 8255

Operations

- PortA: Operate in Mode 0, 1, 2

- PortB: Operate in Mode 0, 1

- PortC: Operate in Mode 0 and PortC is used as the control signals for

PortA and PortB in operation mode 1.




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INITIAL STATE (Reset)

- When reset, three ports of 8255 are set as input port at mode 0.

- To define the operation mode of 8255, we have to set the control word

with the suitable value.Control Word

- This control word will set the direction of ports (input/output) or

operation mode.

- Control word (8 bits) is save in the Control Word Register.

Ex: We choose the operation mode for 8255 like this:

Port A: Input, mode 1; Port B: Output, mode 0, Port C high : output, Port

C low : Input.

The value of CW : 10110001b => B1h




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Outport(dia chi, gia tri)

- C, VC: outportb(0x37B, 0xB1);

- VB: outport(&h37B, &hB1)

A = input(&h37A); The mode bit set/reset of PortC

- Use to set or clear one specific bit of Port C.

- Normally use in the control mode

- The bit set reset of Port C is controlled by CW.

- Specification for CW:

Bit 7: 0

Bit: 6, 5, 4: X

Bit 3 , 2, 1: Choose bit (000 – bit 0 to 111 – bit 7)

Bit 0: = 0: Clear

= 1: Set

Ex: 0 0 0 0 0 1 1 0 Control Word Reg

Outport(&h37B, &h07) set bit 3 of Port C

Outport(&h37B, &h06) clear bit 3 of Port C

The control word of this case is also output to the control word address of

8255.

Note: The bit set/reset mode of port C does not effect to the normal operation

mode of 8255 was set before.

OPERATION MODE

+ Mode 0 (Basic Input/Output)

This functional configuration provides simple input and output operations for

each of the three ports. No handshaking is required, data is simply written to

or read from a specific port.

Mode 0 Basic Functional Definitions:

Two 8-bit ports and two 4-bit ports




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Any Port can be input or output

This mode does not use handshaking with the I/O.

This mode is suitable for the data which are not normally changed. Ex,

this can be used in the getting of sampling rate of data because it does

not check the error of the data.

Input

Output

Mode 1 - (Strobed Input/Output).

This functional configuration provides a means for transferring I/O data to or

from a specified port in conjunction with strobes or “hand shaking” signals.

In mode 1, port A and port B use the lines on port C to generate or accept

these “hand shaking” signals.




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Mode 1 Basic Function Definitions:

• Two Groups (Group A and Group B)

• Each group contains one 8-bit port and one 4-bit control/data port

• The 8-bit data port can be either input or output.• The 4-bit port is used for control and status of the 8-bit port.

INPUT MODE

STB (Strobe Input)

A “low” on this input loads data into the input latch.

IBF (Input Buffer Full F/F)

A “high” on this output indicates that the data has been loaded into the input

latch: in essence, and ack nowledgment. IBF is set by STB input being low

and is reset by the rising edge of the RD input.




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INTR (Interrupt Request)

A “high” on this output can be used to interrupt the CPU/MCU when and

input device is requesting service. INTR is set by the condition: STB is a

“one”, IBF is a “one” and INTE is a “one”. It is reset by the falling edge ofRD. This procedure allows an input device to request service from the CPU

by simply strobing its data into the port.

INTE A

Controlled by bit set/reset of PC4.

INTE B

Controlled by bit set/reset of PC2.

OUTPUT MODE




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OBF – (Output Buffer Full). The OBF output will go “low” to indicate that

the CPU has written data out to be specified port.

Data is guaranteed valid at the rising edge of OBF, The OBF will be set by

the rising edge of the WR input and reset by ACK input being low.

ACK – (Acknowledge Input). A “low” on this input informs the 82C55 that

the data from Port A or Port B is ready to be accepted. In essence, a response

from the peripheral device indicating that it is ready to accept data.INTR - (Interrupt Request). A “high” on this output can be used to interrupt

the CPU when an output device has accepted data transmitted by the CPU.

INTR is set when ACK is a “one”, OBF is a “one” and INTE is a “one”. It is

reset by the falling edge of WR.




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Mode 2 (Strobed Bi-Directional Bus I/O) – Self research

Ex: Using 8255 DLL// FILE: 8255.cpp#include <stdio.h>#include <conio.h> // contains Visual C++'s inp and outfunctions// ------------------------------------------------------// FUNC: Out8255// DESC: uses Microsoft's Visual C++ _outp() function// to output a PortData to PortAddress// ------------------------------------------------------short _stdcall Out8255( int PortAddress, int PortData ){short Dummy; Need Dummy since _outp officiall// back to VB Dummy = (short)(_outp( PortAddress, PortData ));return(Dummy);}; // end of Out8255// ----------------------------------------------------// FUNC: In8255// DESC: uses Microsoft's Visual C++ _inp() function// to read PortAddress// ----------------------------------------------------short _stdcall In8255( int PortAddress ){short PortData;in Win32 C++// use (short) to force returning 16- PortData = (short)(_inp( PortAddress ));return( PortData );}; /* end of In8255 */

Ex: Count from zero to 255 then light up Led




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Visual Basic Code

Option Explicit'Declare use of the DLLPrivate Declare Function Out8255 Lib "8255.dll" (ByValPortAddress As Integer, ByVal PortData As Integer) As Integer

Private Declare Function In8255 Lib "8255.dll" (ByValPortAddress As Integer) As Integer

'Declare variablesDim BaseAddress As Integer: ' 8255 Base AddressDim Dummy As Integer: ' Dummy variable used with DLLDim PortA As Integer: ' 8255 Port A addressDim PortB As Integer: ' 8255 Port B addressDim PortC As Integer: ' 8255 Port C addressDim Cntrl As Integer: ' 8255 Control AddressDim Number As Integer: ' decimal number to count from 1 to 255Dim Start As Integer: ' Start flagDim Msg As StringDim Style As IntegerDim Response As IntegerDim PortSelected As Integer

Private Sub Form_Load()' Program is loaded with these valuestxtOutputWindow.Text = "Enter Base Address"Start = 0: 'Counting action not startedNumber = 0: 'Number to start withoptPortA.Value = True ' Default port is AEnd Sub




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Private Sub cmdGo_Click()If Start = 0 Then' user clicked GO button first timeIf txt8255Address.Text = "" Then' Base address was not defined

Msg = "Enter a Base Address! e.g. 608" ' Define message.Style = vbOK + vbExclamation ' Define buttons.Response = MsgBox(Msg, Style)Exit SubEnd IfStart = 1: ' Go button enabled; start countingcmdGo.Caption = "Pause"' Assign values for all addressesBaseAddress = Val(txt8255Address.Text)PortA = BaseAddressPortB = BaseAddress + 1PortC = BaseAddress + 2Cntrl = BaseAddress + 3' determine which port to output to' default is Port AIf optPortA.Value = True ThenPortSelected = PortAPrint PortSelectedEnd IfIf optPortB.Value = True ThenPortSelected = PortBPrint PortSelectedEnd IfIf optPortC.Value = True ThenPortSelected = PortCPrint PortSelectedEnd If' configure all ports for outputDummy = Out8255(Cntrl, 128)' initialize all Ports to 0Dummy = Out8255(PortA, 0)Dummy = Out8255(PortB, 0)Dummy = Out8255(PortC, 0)ElseStart = 0: ' user clicked GO button againcmdGo.Caption = "Go!"End IfEnd Sub

Private Sub cmdEnd_Click()Beep'txtOutputWindow.Text = "Stopped"Dummy = Out8255(PortA, 0)

Dummy = Out8255(PortB, 0)Dummy = Out8255(PortC, 0)' quit programEnd




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End Sub

Private Sub tmrTimer_Timer()If Start = 1 ThenNumber = Number + 1

Dummy = Out8255(PortSelected, Number)txtOutputWindow.Text = "Number = " + Str(Number)If Number = 255 ThenBeeptxtOutputWindow.Text = "Finished"Dummy = Out8255(PortSelected, 0)Start = 0Number = 0cmdGo.Caption = "Go!"Exit SubEnd If

ElseExit SubEnd IfEnd Sub

Ex: Print out the decimal equivalent of the 8 position Dip switch

Option Explicit'Declare use of the DLLPrivate Declare Function Out8255 Lib "8255.dll" (ByValPortAddress As Integer, ByVal PortData As Integer) As IntegerPrivate Declare Function In8255 Lib "8255.dll" (ByValPortAddress As Integer) As Integer'Declare variablesDim BaseAddress As Integer: ' 8255 Base Address




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Dim Dummy As Integer: ' Dummy variable used with DLLDim PortA As Integer: ' 8255 Port A addressDim PortB As Integer: ' 8255 Port B addressDim PortC As Integer: ' 8255 Port C addressDim Cntrl As Integer: ' 8255 Control AddressDim PortValue As Integer: ' decimal value read at port

Dim PortValue As Integer: ' decimal value read at portDim Start As Integer: ' Start flagDim Msg As StringDim Style As IntegerDim Response As IntegerDim PortSelected As Integer

Private Sub cmdEnd_Click()Beep

'txtOutputWindow.Text = "Stopped"' quit programEndEnd Sub

Private Sub cmdGo_Click()If Start = 0 Then' user clicked GO button first timeIf txt8255Address.Text = "" Then' Base address was not definedMsg = "Enter a Base Address! e.g. 608" ' Define message.

Style = vbOK + vbExclamation ' Define buttons.Response = MsgBox(Msg, Style)Exit SubEnd IfStart = 1: ' Go button enabled; start countingcmdGo.Caption = "Pause"' Assign values for all addressesBaseAddress = Val(txt8255Address.Text)PortA = BaseAddressPortB = BaseAddress + 1PortC = BaseAddress + 2

Cntrl = BaseAddress + 3' determine which port to output to' default is Port AIf optPortA.Value = True ThenPortSelected = PortAEnd IfIf optPortB.Value = True ThenPortSelected = PortBEnd IfIf optPortC.Value = True ThenPortSelected = PortC

End If' configure all ports for inputDummy = Out8255(Cntrl, 155)




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' initialize all Ports to 0ElseStart = 0: ' user clicked GO button againcmdGo.Caption = "Go!"End IfEnd Sub

Private Sub Form_Load()' Program is loaded with these valuestxtOutputWindow.Text = "Enter Base Address"Start = 0: 'Counting action not startedoptPortA.Value = True ' Default port is AEnd SubPrivate Sub tmrTimer_Timer()If Start = 1 ThenPortValue = In8255(PortSelected)

txtOutputWindow.Text = "Value = " + Str(PortValue)End IfEnd Sub

Ex: 8255 connects to ADC0808




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SERIAL COMMUNICATION STANDARD

The electrical specifications of the serial port is contained in the EIA

(Electronics Industry Association) RS232 standard. It states many parameters

such as:

1. A "Space" (logic 0) will be between +3 and +25 Volts.

2. A "Mark" (Logic 1) will be between -3 and -25 Volts.

3. The region between +3 and -3 volts is undefined.

4. An open circuit voltage should never exceed 25 volts. (In

Reference to GND)

5. A short circuit current should not exceed 500mA. The driver

should be able to handle this without damage.




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The com port in a PC has 9 female pins.

Pin No Abbreviation Full Name

Pin 2 RD Transmit Data

Pin 3 TD Receive Data

Pin 7 RTS Request To Send

Pin 8 CTS Clear To Send

Pin 6 DSR Data Set Ready

Pin 5 SG Signal Ground

Pin 1 CD Carrier Detect

Pin 4 DTRData Terminal

Ready

Pin 9 RI Ring Indicator

There are two kinds of serial communication

The speed of transmission is called Baud (bit/s)




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The width of bit also expresses the speed of communication. Ex, the

transmission data has the width of bit is 20ms, this means that it can be

transmit 1/20ms = 50 bit in 1 second. Then, it can be said that the

transmission speed is 50 bit per second or the baud rate is 50bps (bit persecond). Baud (Baud is number of bits transmitted/sec, including start, stop,

data and parity).

Some typical Baud of serial communications: 300, 600, 1200, 2400, 4800,

9600, 19200,….., 56000, 115200,….

Ex: Null Modem

1. SYNCHRONOUS COMMUNICATION

Sender and receiver must synchronize.

Block of data can be sent.

More efficient.

Expensive

Synchronous transmit/receive diagram




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Synchronous transfer does not transfer extra bits. However, it requires

clock signal.

Synchronous transmit/receive diagram

2. ASYNCHRONOUS COMMUNICATION

- Each byte is encoded for transmission.

- No need for sender and receiver synchronization.

Asynchronous transmit/receive diagram




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Asynchronous transfer does not require clock signal. However, it

transfers extra bits (start bits and stop bits, parity bit) during data

communication.

-10 V Mark

+10 V Space

Asynchronous data transfer diagram

In the RS232 standard, logic 1 is named Mark (-10V) and logic 0 is

named Space (+10V). When not active, the transmission line is in the state of Mark.

When starting transmission, the Start bit is transmitted first, then 8 data

bit are followed (The LSB bit is transmit first then the MSB bit is

transmitted in the end).




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3. PORT ADDRESS ON PC

COM1 3F8

COM2 2F8

COM3 3E8

COM4 2E8

4. INTERFACE CHIP

The MAX232 (Figure 4-1) includes two drivers that convert TTL or CMOS

inputs to RS-232 outputs and two receivers that convert RS-232 inputs to

TTL/CMOS-compatible outputs. The drivers and receivers also invert the

signals.

This chip contains two charge-pump voltage converters that act as tiny,

unregulated power supplies that enable the chip to support loaded RS-232

outputs of ±5V or greater. Four external capacitors store energy for the

supplies. The recommended value for the capacitors is 1μF or larger. If using




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polarized capacitors, take care to get the polarities correct when you put the

circuit together.

The voltage at pin 6 is negative, so its capacitor’s + terminal connects to

ground. Because the outputs can be as high as 10V, be sure the capacitors arerated for a working voltage direct current (WVDC) of at least 15V.




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5. PROGRAMMING SERIAL COMMUNICATION USING PC

The controller of the serial communication on PC is called UART (Universal

Asynchronous Receiver Transmitter). Some typical UART controllers are:

8250, 8250A, 16550, 16650, 16750,…

In these UART controller, we just focus on some registers supply for

programming PC.




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Base Address DLAB Read/Write Abr. Register Name

+ 0

=0 Write - Transmitter Holding Buffer

=0 Read - Receiver Buffer

=1 Read/Write - Divisor Latch Low Byte

+ 1=0 Read/Write IER Interrupt Enable Register

=1 Read/Write - Divisor Latch High Byte

+ 2- Read IIR Interrupt Identification Register

- Write FCR FIFO Control Register

+ 3 - Read/Write LCR Line Control Register

+ 4 - Read/Write MCR Modem Control Register

+ 5 - Read LSR Line Status Register

+ 6 - Read MSR Modem Status Register

+ 7 - Read/Write - Scratch Register

DLAB (Divisor Latch Access Bit) is the bit 7 of LCR

0: Programming data frame

1: Programming communication speed.

User can reprogramming the communication speed by reload the value of

divisor of the UART.

Divisor = Clock frequency/(speed x 16)

Ex: UART uses clock has frequency of 1.8432MHz and the desired speed is

9600 bauds. Then, the divisor is:

Divisor = 1843200/(9600 x 16) = 12

+ SOME TYPICLE REGISTERS

LINE CONTROL REGISTER - LCR (+3)

Bit 7 1 Divisor Latch Access Bit




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0Access to Receiver buffer, Transmitter buffer &

Interrupt Enable Register

Bit 6 Set Break Enable

Bits 3, 4 And

5

Bit

5

Bit

4

Bit

3Parity Select

X X 0 No Parity

0 0 1 Odd Parity

0 1 1 Even Parity

Bit 2 Length of Stop Bit

0 One Stop Bit

12 Stop bits for words of length 6,7 or 8 bits or 1.5 Stop

Bits for Word lengths of 5 bits.

Bits 0 And 1 Bit

1

Bit

0 Word Length

0 0 5 Bits

0 1 6 Bits

1 0 7 Bits

1 1 8 Bits

Opencom(‘Com4’, 9600, 8, N, 1) TX

Opencom(‘Com7’, 9600, 8, N, 1) RX

E: even

O: odd

PARITY

A parity bit is a bit that is added to ensure that the number of bits with the

value one in a set of bits is even or odd. Parity bits are used as the simplest

form of error detecting code.

There are two variants of parity bits: even parity bit and odd parity bit.

When using even parity, the parity bit is set to 1 if the number of ones in a

given set of bits (not including the parity bit) is odd, making the entire set of

bits (including the parity bit) even. When using odd parity, the parity bit is set

to 1 if the number of ones in a given set of bits (not including the parity bit) is

even, keeping the entire set of bits (including the parity bit) odd.

http://en.wikipedia.org/wiki/Bit

http://en.wikipedia.org/wiki/1_(number)

http://en.wikipedia.org/wiki/Even_number

http://en.wikipedia.org/wiki/Odd_number

http://en.wikipedia.org/wiki/Error_detection_and_correction



http://en.wikipedia.org/wiki/Odd_number

http://en.wikipedia.org/wiki/Even_number

http://en.wikipedia.org/wiki/1_(number)

http://en.wikipedia.org/wiki/Bit




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However, parity has the advantage that it uses only a single bit and requires

only a number of XOR gates to generate.

If an odd number of bits (including the parity bit) are transmitted incorrectly,

the parity bit will be incorrect and thus indicates that an error occurred intransmission. The parity bit is only suitable for detecting errors; it cannot

correct any errors, as there is no way to determine which particular bit is

corrupted. The data must be discarded entirely, and re-transmitted from

scratch.

Ex: The parity bit can be computed as follows, assuming we are sending a

simple 4-bit value 1001 with the parity bit following on the right, and with ^

denoting an XOR gate:

Transmission sent using even parity:

A wants to transmit: 1001

A adds parity bit and sends: 10010

A computes parity bit value: 1^0^0^1^0 = 0

B receives: 10010

B computes parity: 1^0^0^1^0 = 0

B reports correct transmission after observing expected even result.

Transmission sent using odd parity:



A computes parity bit value: 1^0^0^1^1 = 1

B receives: 10011

B computes overall parity: 1^0^0^1^1 = 1

B reports correct transmission after observing expected odd result.

http://en.wikipedia.org/wiki/XOR_gate



http://en.wikipedia.org/wiki/Transmission_(telecommunications)


http://en.wikipedia.org/wiki/Automatic_repeat-request






http://en.wikipedia.org/wiki/Transmission_(telecommunications)





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Transmission sent using even parity:



A computes parity bit value: 1^0^0^1^0 = 0*** ERROR CASE ***

B receives: 11010


B reports incorrect transmission after observing unexpected odd result.

B calculates an odd overall parity indicating the bit error. Here's the same

example but now the parity bit itself gets corrupted:


A computes even parity value: 1^0^0^1 = 0

A sends: 10010

*** ERROR CASE ***

B receives: 10011


B reports incorrect transmission after observing unexpected odd result.

Special case


A computes even parity value: 1^0^0^1 = 0

A sends: 10010

*** ERROR CASE***

B receives: 11011


B reports correct transmission though actually incorrect.

If there are two bits error, parity can not check!




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LINE STATUS REGISTER - LSR (+5)

Bit Notes

Bit 7 Error in Received FIFO

Bit 6 Empty Data Holding Registers

Bit 5 Empty Transmitter Holding Register

Bit 4 Break Interrupt

Bit 3 Framing Error

Bit 2 Parity Error

Bit 1 Overrun Error

Bit 0 Data Ready

Bit 0 = 1: UART receive 1 character

INTERRUPT IDENTIFICATION REGISTER - IIR (+2)

Bit Notes

Bits 6 and

7

Bit

6

Bit

7

0 0 No FIFO

0 1 FIFO Enabled but Unusable

1 1 FIFO EnabledBit 5 64 Byte Fifo Enabled (16750 only)

Bit 4 Reserved

Bit 3 0 Reserved on 8250, 16450

1 16550 Time-out Interrupt Pending

Bits 1 and

2

Bit

2

Bit

1

0 0 Modem Status Interrupt

0 1 Transmitter Holding Register EmptyInterrupt

1 0 Received Data Available Interrupt

1 1 Receiver Line Status Interrupt

Bit 0 0 Interrupt Pending

1 No Interrupt Pending

INTERRUPT ENABLE REGISTER – IER (+1)Bit Notes




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Bit 7 Reserved

Bit 6 Reserved

Bit 5 Enables Low Power Mode (16750)

Bit 4 Enables Sleep Mode (16750)

Bit 3 Enable Modem Status InterruptBit 2 Enable Receiver Line Status Interrupt

Bit 1 Enable Transmitter Holding Register Empty Interrupt

Bit 0 Enable Received Data Available Interrupt

MODEM CONTROL REGISTER – MCR (+4)

Bit Notes

Bit 7 Reserved

Bit 6 Reserved

Bit 5 Autoflow Control Enabled (16750 only)

Bit 4 LoopBack Mode

Bit 3 Aux Output 2

Bit 2 Aux Output 1

Bit 1 Force Request to Send

Bit 0 Force Data Terminal Ready




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Ex: Transmit/Receive serial data

#include <dos.h>

#include <stdio.h>

#include <conio.h>#define PORT1 0x3F8

void main(void)

{

int C;

int ch;

outportb(PORT1 + 1, 0) ; // Not using interrupt on Port1

outportb(PORT1 + 3, 0x38); // Set Dlab on

outportb(PORT1 + 0, 0x3) ; //Set baud rate – divisor latch low byte

// Default 0x03 = 38400 bps

// 0x01 = 115200 bps

// 0x02 = 56700 bps

// 0x06 = 19200 bps

// 0x0C= 9600 bps

// 0x18 = 4800 bps

// 0x30 = 2400 bps

outportb(PORT1 + 1, 0x00) ; //Set baud rate – divisor latch high byte

outportb(PORT1 + 3, 0x03) ; //8 bit, No parity, 1 stop bit

outportb(PORT1 + 2, 0xC7) ; // Enable FIFO

outportb(PORT1 + 4, 0x0B) ; //Turn on DTR, RST, and OUT2

do {

c = inportb(PORT1 + 5); // Check data is received or not

if (c & 1) {ch = inportb(PORT1);}




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if (kbhit()) {

ch = getch();

outportb(PORT1, ch);}

}while (ch != 27);

}




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EXERCISE:

Using COM Port control many actuators

Type

Documents

PC Interfacing Lecture - 09-2013