1 About communication
Roche Diagnostics
COBAS INTEGRA 400 plus analyzer/Cedex Bio HT Analyzer · Software version 3.6/5.1 · Host Interface Manual · Version 1.24
22
Communication control
Flow control (hardware/software handshake)
If the instrument or the host is currently not able to
receive data, it must be able to stop the communication.
This is done by the flow control.
There are two possibilities, either hardware handshake or
software handshake.
Suggestion: Software handshake simplifies RS-232 cable
wiring and host SW handling.
u
Related topics
• About the handshake (197)
• About the RS-232 cable (186)
Sequence counter and block check sum
Sequence counter
The sequence counter (SC) is a one digit number, which
alternates between 0 and 1. The SC is used by the host to
initiate retransmit of data. The host's SC must be
synchronized to the instrument's SC. Both SCs (host and
instrument) must be updated simultaneously, otherwise a
sequence error will occur
f
instrument will retransmit its
previous message.
The mathematical presentation appears as follows:
z
1
Block check sum
The block check sum (BCS) is a 3-digit, ASCII-coded
number.
The BCS contains the sum of all values of the message
starting with <SOH> ... to <SC> (<CR>) <LF> modulo
1000.
z
2
If any mismatch occurs, the receiving station has to react
accordingly.
Enable / disable of the SC and BCS can be done in the
Host Interface Configuration
menu (either both BCS
and SC exist or neither).
q
We strongly recommend that you enable the block
check. Otherwise you cannot be sure that all data are
correctly transmitted.
SC
(inc SC) mod 2
=
BCS
sum (ord(<SOH>) .. ord(<LF>)) mod 1000
=
