S5-95U, Second Serial Interface
ASCII Driver
•
Receiving
The communication partner sends data to the SI2 interface of the S5-95U in ASCII code. The
data is buffered in the input buffer and stored in the receive mailbox (EF) after initiation through
the PLC program.
e.g.:
- An S5-95U sends data to a printer. (Data traffic in one direction)
- An S5-95U receives data from a barcode reader. (Data traffic in one direction)
- An S5-95U receives and sends data to a terminal (keyboard). (Data traffic in 2
directions)
Characteristics of send mailbox and receive mailbox:
•
Send mailbox and receive mailbox can be stored in a data block or in the flag area.
•
1024 bytes of the input buffer are available in all modes ( Section 4.4).
•
In those modes in which the characters XON, XOFF, RUB OUT are interpreted when received,
the ASCII driver can receive data and/or frames even after it has sent an XOFF character to the
communication partner. In this case, the ASCII driver receives data until the input buffer is full or
it receives frames until the maximum possible number of frames is reached.
Example of a
”
borderline case
”
:
If a received frame is 1024 bytes long and the ASCII driver consequently sends XOFF,
characters which were received by the communication partner after transmitting XOFF cannot be
buffered any more.
•
In mode 1, 7 or 8 ( Section 4.4), you must specify the amount of data to be sent (in bytes) in
the first word of the send mailbox.
You parameterize the position of send mailbox and receive mailbox in DB1 ( Section 4.4).
EWA 4NEB 812 6095-02
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