CCJIMUNICATIONS
6,7,2
6,7,2,1
VER.V09F
TABLE 6.2 TECHINCAL IMPLEMENTATION
Synchronous transmission using Bisync.
Character set - EBCDIC
SECTION 6.7
Full CRC generation, error handling and flow control.
Modem handshake lines available.
Internal or external clocking options,
May be used over the public switched telephone network or
private lines.
Records terminated using the EM character, providing optimum
throughput.
The m,fait acknowledge" is fully impleirented.
Protocol use is completely transparent to user programs.
Data Rates - up to 9600 Hz with external clocking.
- up to 4800 Hz using internal clocking
The internal self-synchronising feature enables HUNTER to HUNTER
communications over standard 300 baud asynchronous r.1odems,
SYNCHRONOUS COMMUNICATION
Synchronous communication transfers data as a continuous stream
of data characters, without the need for start and stop bits as
used in asynchronous communication. This maximises the data
transfer rate for a given channel bandwidth. For the receiver
to be able to use the data two levels of synchronisation need to
take place:
i) Bit Synchronisation
This allows the receiver to save the state of each bit
correctly, preferably sampled at the centre of each bit,
ii)
Character Synchronisation
Each block of eight bits which represent a charcicter needs
to be identified froJ1 within the data streat~.
Bit Synchronisation
Two techniques are used by HUNTER to achieve bit
synchronisation.
External Clocking allows both trans~it and receive to be
synchronised usin~ two independent clockin~ si~nals. These
si1nals are generated by ei thcr a mod~r,; or inode:-11 clin;inator.
The selectio;1 'CU(' on the speed selection ::,f t.r::1:;mi t or
rciceive menus selects this i:1ode.
T·.,o pins are proviciej for
U1,2 cloc'., sircnals. Pin 15 provUcs
the tran:i,ait clock and pLl
17 the recei v2 cloc'.:.
PAGE 6 - 13
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