Description Of Operations; Buffer Configuration - Jetter JetWeb JX2-PR0FI1 Operator's Manual

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JX2-PROFI1

6.1

Data exchange between the user program and the PROFIBUS master is carried out

via input and output registers. Each of these registers contains a data word of 16 bit.

In order to keep the user program as flexible as possible, the memory area, to which

this registers are to belong, is freely selectable. Two registers have been made

available for this purpose. One register contains the start address of the respective

memory area, the other register contains the number of data registers. This way, the

input data starting from register 1m300, for example, and the output data starting

from register 1m400, can be positioned.

As up to 122 input registers can be used, the memory areas would overlap in a

configuration as the one described above. In order to avoid this, the configuration of

the buffers can now be altered as well. The sketch below is to illustrate the interplay

of the registers:

Fig. 7: Structure of the input and output buffers

The address range of registers 1m300 through 1m999 is freely available to the user.

The data buffers can be freely distributed within this range. Letter m stands for the

module number, which is dependent on the configuration of the controller.

The buffers may only be configured during the initialization phase. Under any other

circumstances, the structure of the buffers cannot be changed. This is to keep the

user from making access to a register which has not been defined.

When the user alters one of the buffer configuration registers, a check-up will be

made to ensure that the changed buffer configuration is correct. Among other

features, overlapping of various ranges and exceeding the permitted maximum

widths will be checked. In case an error has occurred in this process, it will be

displayed both in the error register 1m134 and in the error LED.