Appendix E:
OsmoPRO MAX LIS Specification
87
OsmoPRO MAX Automated 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.
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
1
standards with signal levels and data transmission
rates defined by the IEEE
2
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
568D.
•
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, users can
configure the instrument as either the client or the server
in establishing the TCP/IP connection.
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.
1 American National Standards Institute
2 Institute of Electrical and Electronics Engineers
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.
Transfer phase:
In transfer phase, the sender transmits
messages to the receiver in frames. Each frame contains
a maximum of 64,000 characters including frame
overhead.
Although the LIS01-A2 standard states long messages
can be sent by being broken up into multiple frames, the
instrument software is not currently configured to handle
this situation. A frame starts with the
<STX>
character
(ASCII decimal 2), followed by a frame number which is a
single digit from 0 to 7. The first frame in a transfer
begins with frame number 1 and is incremented for each
successive frame until it reaches 7. After frame 7, the next
frame is given a number of 0, and continues to increment
as above.
The frame number is used to distinguish between new
and re-transmitted frames. The message part is
terminated with the
<ETX>
character (ASCII decimal 3),
followed by the checksum (see below) and
<CR><LF>
.
Checksum:
The checksum indicates if a frame is
defective. It is encoded as two ASCII characters and is
computed by adding the ASCII decimal values of all the
characters in the frame starting with the frame number
and ending with the
<ETX>
character. Only the least
significant 8 bits are kept and are converted to
hexadecimal digits making up the two ASCII characters.
Acknowledgment:
The sender waits for an
acknowledgment from the receiver after each frame is
sent. There is a timeout of 15 seconds upon receiving the
acknowledgment.
