Texas Instruments 990 User Manual page 14

I ntroducti on
*
A secondary station. This may be either a Model 990/5
Computer system or a remote processing device, such as
a
TM990 or PM550 system. If the secondary station is a
Model 990/5 Computer system, it must
be
equipped wi th
the following:
A
TX5 operating system, release 3.2.0,
communications package software
with
A
local-line module (LLM), which functions as the
communications controller
A DXlO HDLC Communications Package ROM
loader to
provide downloading capabilities
*
A
communications line that interconnects the computers
within the network. This can be one of the following:
A
local-line cable consisting of a single-
shielded, twisted-pair cable that is a maximum of
3000 meters in length
A
modem line in accordance wi th
EIA
specification
RS-232C.
A
configuration can include a maximum of 32 secondary stations
connected to the primary station on a single multi};X)int line, as
shown in Figure 1-1. The secondary stations can be any
combination of TXS supported systems or remote devices.
The physical interface between the primary and secondary stations
is provided by the FCCC board in the
pr lmary station
line to the LLMs or
at the secondary
interconnected through the communications
other type of communications controller
stations. Features of the FCCC board and
in subsequent paragraphs of this section.
the LLM are described
Control of the networ k
Secondary stations can
Each secondary station is
secondary station must
before sending any data.
is provi ded by the pr imar y st ati on.
send data only to the primary station.
J;X>lled on a time-selected basis.
A
wait until it is polled by the primary
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