Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 1
Transmission Modes:
either Parallel
or Serial
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 2
1000000 1
Transmission Mode: Serial
Serial transmission of one 8-Bit ASCII Character
Bits of a character are transmitted one at a time.Only a single channel is required.
Transmitter Receiver
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 3
0 1
Transmission Mode: Serial
Serial transmission of one 8-Bit ASCII Character
Bits of a character are transmitted one at a time.Only a single channel is required.
ReceiverTransmitter
1 0 0 0 0 0
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 4
Transmission Mode: Serial
Serial transmission of one 8-Bit ASCII Character
Bits of a character are transmitted one at a time.Only a single channel is required.
Transmitter0 0 1
Receiver1 0 0 0 0
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 5
Transmission Mode: Serial
Serial transmission of one 8-Bit ASCII Character
Bits of a character are transmitted one at a time.Only a single channel is required.
Transmitter0 0 0 1
Receiver
1 0 0 0
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 6
Transmission Mode: Serial
Serial transmission of one 8-Bit ASCII Character
Bits of a character are transmitted one at a time.Only a single channel is required.
Transmitter0 0 0 0 1
Receiver
1 0 0
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 7
Transmission Mode: Serial
Serial transmission of one 8-Bit ASCII Character
Bits of a character are transmitted one at a time.Only a single channel is required.
Transmitter0 0 0 0 0 1
Receiver
1 0
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 8
Transmission Mode: Serial
Serial transmission of one 8-Bit ASCII Character
Bits of a character are transmitted one at a time.Only a single channel is required.
Transmitter0 0 0 0 0 0 1
Receiver
1
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 9
Transmission Mode: Serial
Serial transmission of one 8-Bit ASCII Character
Bits of a character are transmitted one at a time.Only a single channel is required.
Transmitter1 0 0 0 0 0 0 1
Receiver
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 10
10000001#1
Transmission Mode: Parallel
Parallel transmission of four 8-bit ASCII character
All bits of a character are transmitted simultaneously.Each bit has a separate channel dedicated to it.
Transmitter Receiver
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 11
Transmission Mode: Parallel
Parallel transmission of four 8-bit ASCII character
All bits of a character are transmitted simultaneously.Each bit has a separate channel dedicated to it.
Transmitter Receiver
10001010#2
10000001#1
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 12
Transmission Mode: Parallel
Parallel transmission of four 8-bit ASCII character
All bits of a character are transmitted simultaneously.Each bit has a separate channel dedicated to it.
Transmitter Receiver
10011000#3
10001010#2
10000001#1
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 13
Transmission Mode: Parallel
Parallel transmission of four 8-bit ASCII character
All bits of a character are transmitted simultaneously.Each bit has a separate channel dedicated to it.
Transmitter Receiver
10100001#4
10011000#3
10001010#2
10000001#1
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 14
There are two common forms of serial transmission:- Asynchronous- Synchronous
Bit and character Synchronization: The receiver must correctly interpret the bit pattern generated by the transmitter if there is to be a meaningful exchange of information.
There is a need to periodically Resynchronize.
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 15
Two ways to perform this - - Asynchronous Transmission where the transmitter and receiver are resynchronized at the beginning of each character, or
Synchronous Transmission where timing signals are set throughout the network, permitting the receiver to derive a clock that is precisely in step with the transmitter clock.
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 16
Asynchronous Transmission
The "1" state or "Mark" condition is when current is flowing,andThe "0" state or "Space" condition is when current is not flowing.
The receiver mechanism is started by changing the date communication line from the idle state "1" to the "0" state for the length of time it takes to transmit one bit.
This is called the Start Bit.
The line is then changed, or conditioned, to a "1" bit or "0" bit to represent each bit in the character being sent.
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 17
Asynchronous Transmission
Following the character bits, one or more bits times of 1 state (idle) are sent to allow the receiver to coast back down to a known position in time for the start bit of the next character.
The first 1 bit following the character bits is called the Stop Bit.
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 18
Asynchronous Transmission of Two 8-Bit Characters
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
1 1 1 1 0 1 0 0 1 0 1 1 0 1 1 1 1 1 0 1 1 1 1 0 0 1 1 1 1 1 1 1 1
Idle Line one 8-bit character
Idle Line Idle Lineone 8-bit character
10 bits required to transmit one 8-bit EBCDIC character.
startbit
stopbit
startbit
stopbit
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 19
Asynchronous Transmission is also called
Start/Stop Transmission
There is no fixed time interval between characters except for the requirement that the line be idle for at least the stop bit interval. The stop bit is necessary to guarantee that each character will begin with a 1 or 0 transition to clearly define the start of each character.
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 20
Asynchronous
n The start of each character, or block of characters is arbitrary; once started the time of occurrence of each signal representing a bit within the character, or block has the same relationship to significant instants of a fixed time frame.
n All bits of a character are synchronized and occur at a set interval. However, different characters within a message are not synchronized with each other.
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 21
Asynchronous Mode Characteristics
n Data may have a period of inactivity between characters of a message.
n Start and stop bit(s) frame each character.
n Bits within a character are sent at prescribed time intervals synchronized with the start bit.
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 22
Asynchronous Mode Characteristics (Continued)
n Allows timing to be established independently in transmitting and receiving station.
n Transmission time is increased by the time required to transmit start and stop bits.
Character size = Data bits+ Start bits+ Stop bits
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 23
P bit
Stop
1
1.5
2
StartBit
Idle stateof line
Odd/Evenor Unused
Remain idleor next start bit
5 to 8 data bits
1 1 1 1 000 1 00 1 0 11 00 1 0 0 0 1 0 1 0
(b) 8-bit asynchronous bit stream Idle line
~~ ~~
Start bit 1st Char
Stop bit
Start bit
Random time interval between characters
2nd Char
Stop bit
3rd Char
(a) Data character format
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 24
n Synchronous Transmission: is used for high-speed transmission of a block of characters.
Start/Stop bits are not required for each character. Instead, synchronization is established by sending synchronization characters prior to each block of message bits.
This is accomplished by either a separate clock lead from the transmission point to the reception point, in addition to the data lead, or a modem that includes the clock information in the modulation process the encodes the data.
Synchronous transmission permits more information to be transmitted per unit of time than asynchronous transmission because fewer total bits are required to send a long message.
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 25
Synchronous Transmission of One Block of Data
Transmitter ReceiverData Message SynChar
SynChar
SynChar
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 26
Synchronous Mode
n Synchronous data transmission mode in which the time of occurrence of each signal representing a bit is related to a fixed time frame.
n All bits of character are synchronized and all characters within a message are synchronized with each other.
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 27
Synchronous Transmission:
n Once bit synchronization is achieved, character synchronization must be accomplished.
n Character synchronization is simply a matter of knowing how many bits are required to form one character.
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 28
Synchronous Mode Characteristics
n The bits of one character are followed immediately by those of the next and are transmitted at the maximum line speed.
n Bit synchronization, which ensures that the receiving station knows at what instant a bit starts and ends, is provided by control timings.
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 29
Synchronous Mode Characteristics (Continued)
n Character synchronization which ensures that the receiving station knows which bit is in which character is achieved by transmitting two or more unique synchronization codes (SYN) at the beginning of each message.
n If there are data character gaps, it will be filled by SYN characters to maintain continuity of transmission.
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 30
0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 0 0 0 0 0 1 0 0 1 0 0 0 0 1 0
Sync Sync Sync A B
Synchronous Mode
Transmission Mode 8 Copyright 1998, Professor John T. Gorgone 31
Syn Syn Syn
One or more SYN characters
Control characters Data characters Control characters
~~ ~~~~ ~~
F F
Control fields Control fieldsData field
8-bitflag
8-bitflag
(a) Character - oriented frame
(b) Bit - oriented frames
SYNCHRONOUS TRANSMISSION