VIPA SSM-BG41, Manual

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Handling with VIPA data handling blocks Manual BG41/BG42/BG43
4-18 Rev. 99/49
4.1.6 Data handling with procedure STX/ETX
The interfaces of the building blocks BG41, BG42 and BG43 can be operated with the procedure
STX/ETX, if this function is selected in FB100 or FB101. The STX/ETX procedure is used for the
transmission of ASCII characters (20h…7Fh). It operates without a block check (BCC). If data is to
be read in from the periphery, the start character STX (02h) must be available. The characters to be
transferred follow. The end character must be ETX (03h). The useful data, i.e. all characters
between STX and ETX, is transferred to the automation device after the end character ETX has
been received.
When sending the data from the PLC to a peripheral device, the useful data is transferred to the
building block and from there transferred to the external device with STX as the start character and
ETX as the end character.
The data handling blocks FB 43 and FB 44 come together with the PLC.
4.1.6.1 FB40 (PARA_STX), parametrizing of the STX/ETX procedure
With FB40, the function for reparametrizing the STX/ETX procedure is selected.
The following parameters are to be transferred when loading FB40:
Des. Format Explanation
ADR KY Building block’s absolute base
address
K/M KY Number of channels/ FIFO-Mode
STX KY Start character
E1/2 KF End character 1/end character 2
ZVZ BY Character delay time
FEHL KH Error byte
Tab. 4-9: List of parameters for the loading of FB40
The following details are necessary for the abovementioned parameters:
ADR
(absolut) Input the physical start address, under which the building block can be accessed
by the PLC. This start address can be set with DIL swiches S1 and S2
(see chapter 5).
K/M K = Number of channels, whose STXC/ETX protocol should be parametrized.
M = FIFO Mode.
0 This mode only saves the actual telegram. An old telegram, which has
not yet been collected, will be erased.
1 With this mode all telegrams up to the maximum buffer size are saved.
Telegrams, which can no longer be written into the buffer, will be
chopped.
STX
ASCII character of the new start identifier. Enter in right byte.