Baumer GK473 - Manual (Page 25)

Manual_GK473_S7_Profibus_EN.doc 25/32 Baumer IVO GmbH & Co. KG
04.05.11 Villingen-Schwenningen, Germany
4.2 The global variables, data block DB99
Since many functions are called off repeatedly and the variables defined in the local function blocks
are valid for calling operations only they are stored in data block 99. This way they can be accessed
any time. The chart below gives on overview on the stored variables.
4.3 Busy bit, Timeout bit and Error bit
All functions awaiting an SPA reply will come with a Busy bit, Timeout bit and an Error bit.
Busy bit
The Busy bit indicates that the SPA has not yet replied and that the function has to be repeated. The
true command of the function is not transferred twice but it is only checked whether recent data are yet
available at the gateway. Function polling goes together with setting of Busy bit to make sure
that the function is really repeated until the Busy bit is not active anymore.
Timeout bit
No new data provided within the time window defined will result in setting the Timeout bit what is done
by a timer that is started upon command transfer.
Error bit
In case system functions SFC14 or SFC 15 signalize a polling error latter is stored and can be verified
by the operator. The error bit indicates that an error has occurred.