EUCHNER HBAS 094594 - Handbuch (Seite 51)

EUCHNER Hand-Held Pendant Station HBAS-094594
095640-02-02/06 Subject to technical modifications Page 11 / 40
4. Priorities on a data collision
The term data collision is used when a user receives an STX character while the
user itself is trying to send an STX character. I.e. both users are sending the STX
character at the same time.
To negotiate this data collision, the behavior of the HBAS on the occurrence of a collision
can be set.
Either the hand-held pendant station has priority, that is the HBAS sends its data first and
then receives the data from the control system, or the control system has priority and the
data from the control system are received first and then the data sent to the control system.
This setting is set either in the Configuration (Konfiguration) menu (see section 5) or
as a parameter using parameter transfer (section 9).
Priority: "Control system"
The transmitter in the control system has high priority.
The transmitter in the HBAS has lower priority.
In the case of a data collision, this means that the HBAS detects an STX character when it
is also sending an STX to the control system, it interrupts its transfer and first receives the
data from the control system.
The data transfer to the control system is then repeated.
Example of a possible collision:
HBAS sends a key change STX DLE ??
The control system sends "LCD text" STX DLE ??
Solution:
First the control system sends and then the HBAS sends
HBAS STX DLE DLE STX 31H DLE ETX BCC
Control
system
STX 6CH 25H DLE ETX BCC DLE DLE
Priority: "HBAS"
The transmitter in the HBAS has high priority.
The transmitter in the control system has lower priority.
In the case of a data collision when the HBAS detects an STX character while it is
also sending an STX character, the control system must also detect the collision and
acknowledge the data transfer initiated by the HBAS with a DLE character. Only after
the successful completion of the data transfer, the control system can start its data
transfer.