Siemens SIMATIC S5 CP 523 Manual page 107

CP 523
7 Communications Mode
In Communications mode, the CP 523 permits transfer of a frame of up to 256 bytes between the
CPU and a peripheral device connected to the CP 523 in response to a CPU job request:
• Communication with a terminal device (terminal, barcode reader, keyboard...)
• Point-to-point connection to another CP 523 or a CPU 944
7.1 General
You can choose between the following:
• Transparent mode
The CP 523 does not interpret any characters in Transparent mode.
- No XON/XOFF protocol is possible.
- Only fixed-length message frames can be received. Exception: If you program very skillfully,
you can also receive variable-length frames by evaluating "ZVZ" (i.e. character time-out)
( 7.4.2 under the heading "character time-out").
• Interpretive mode
The CP 523 evaluates the following characters in Interpretive mode:
- RUB OUT (7F
H
- BACKSPACE (08
- XON / OFF character (if programmed)
- 1 or 2 end characters
• 3964(R) mode
The CP 523 interprets the following characters in 3964(R) mode:
- DLE (10
- STX (02
- NAK (15
- ETX (03
During the parameter setting phase, you can also specify whether the data frames are to be
transferred with or without a block check character. The block check character (BBC) increases
transmission reliability. A distinction is made between 3964R and 3964 mode, depending on
whether you want to transfer data with or without a block check character.
- With block check character:
- Without block check character:
The CP 523 handles data transfer with the peripheral device autonomously.
The CPU initiates data exchange between the CPU and the CP by sending a job request. See 7.6
and 7.7 for a detailed description of the data exchange procedure.
See Chapter 8 for a description of function blocks which allow user-friendly handling and control
of data exchange.
The time of day can be read from the integral clock by the CPU in Communications mode and used
in the application program for date-dependent and time-dependent tasks.
Message text printout and editing as in Print mode is not possible in Communications mode. For
this reason, no memory submodule is required in Communications mode.
EWA 4NEB 811 6044-02a
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3964R
3964
Communications Mode
7-1