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Appendix E
OsmoTECH XT LIS Specification
84
OsmoTECH XT Single-Sample Micro-Osmometer User Guide
Manual mode
The instrument can be configured to require an operator
to verify a result before it is sent to the LIS system. The
operator uses the Results screen to verify the result and
initiate the sending operation. This mode works with
either the bidirectional mode or unidirectional mode as
described above.
E.4 Low-level protocol
Physical layer
The instrument can communicate with a LIS using the
TCP/IP protocol. All communications are expected to use
the character bit sequence, structure, and parity sense
definitions defined by the X3.15-1976 and X3.16-1976
ANSI
2
standards with signal levels and data transmission
rates defined by the IEEE
3
802.3 standard.
•
Any speed 10 MB/s or higher is acceptable.
•
The physical connection to the instrument is with a
commercial RJ45F style connector located on the
back of the instrument.
•
Use Category 5 cabling as defined by ANSI EIA/TIA
568A.
•
Use a hub or switch to connect to a laboratory
network, or a connect to a dedicated host computer
using a
cross-over
CAT-5 cable.
Deviating from the LIS01-A2 protocol, the instrument can
be configured as either the client or the server in
establishing the TCP/IP connection.
To configure the instrument as a client or server, press
> SETTINGS > NETWORKING
and then press the
LIS
tab.
•
If the instrument is the client (usual case), configure
the IP address and port (default 13003) of the host
computer.
2 American National Standards Institute
3 Institute of Electrical and Electronics Engineers
•
If the instrument is the server, only the port number
can be configured (default 13004).
Data link layer
The instrument uses the data link layer protocol
described in LIS01-A2 to establish the connection and
handle error and timeout conditions. The three phases of
this protocol are
establishment
,
transfer
, and
termination
,
(described below).
At any point, either system can be the sender, with the
other side being the receiver. In unidirectional mode, the
instrument is always the sender and the LIS is always the
receiver. When neither system is actively transferring
data, the link is in a
neutral state
.
Establishment phase:
The system with information to
transmit initiates the establishment phase, which can
only occur when the link is in the neutral state. A single
<ENQ>
character (ASCII decimal 5) is used to start this
phase.
The only valid responses to the
<ENQ>
character are:
•
<ACK>
(ASCII decimal 6)
–
If
<ACK>
is received, the
phase is complete and the initiating system becomes
the sender.
•
<NAK>
(ASCII decimal 21)
–
If
<NAK>
is received, the
other system is probably busy handling other requests.
•
<ENQ>
–
The initiating system waits 10 seconds and
tries sending
<ENQ>
again. The receiving system can
also have data to transfer and may send
<ENQ>
at the
same time. This is called
line contention
and is handled
differently by the instrument than by the LIS.
–
The instrument waits 1 second and then tries
initiating the establishment phase again.
–
The LIS should wait a minimum of 20 seconds or
until it sees the link being in the neutral state before
trying the establishment phase again.