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If the master requires more data than there is space for in the reserved registers, their
length will automatically be shortened to the maximum possible length.
7.3
If the master has transmitted a "Write Data Block" request, bit 5 is set in the status
register. Now the programming tool is able to react. Out of register 1m118, the
number of bytes can be read which have been written into the data registers by the
master.
Note!
The master causes the slot address to be entered into register 1m121 and the index
of the dat block that is to be written into register 1m123 by the master.
The user will then be able to read the data out of the respective data registers and to
confirm them to be valid by issuing command 13. If the user does, for example, not
want to meet the "Write Data Block" request, because he does not want to operate
the required slot address, he can inform the master by issuing command 14.
Not before one of these commands has been transmitted, bit 5 of the status register
will be cleared. If the master is going to write more data than there will be room for in
the reserved registers, an error message will automatically be sent to the master,
whereas bit 5 will not be set.
7.4
On principle, the user should only access these data ranges if requested by the
master. If it is still necessary to occupy the data range with data, even before a
request has been made by the master (e.g. for very time-critical applications), this
may only be done, if bit 6 has not been set in the status register. This bit is there to
indicate that the operating software of the JX2-PROFI module is accessing data at
that moment. In order to keep up data integrity, the possibility of access to these data
ranges will be ignored during this application, whereas bit 7 is set in the status
register.
The following charts are to illustrate the time characteristics of the respective
services:
Jetter AG
Description: "Write Data Block"
In each data register, there are two bytes.
Access to the data registers of the
acyclic services besides a request
made by the master
JetWeb
47
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