Dascom LA550W User Guide - Manual (Page 135)

User guide Interfaces
127
Protocols
Memory mode XON/XOFF The received characters are stored in a FIFO buffer (first in/first out).
The characters are processed in this buffer.
The buffer capacity can be adjusted from 0 to 64 Kb.
If the buffer is full, the interface signals NOT READY (signal acknow-
ledgement: Level 1, -12 V) and XOFF (hex. 13, dec. 19). This results
in stopping the data transmission. When the FIFO buffer is empty
again, the interface signals READY (level 0, +12 V) and XON (hex.
11, dec. 17). Data transmission can be continued.
In addition, the READY signal is influenced by the status of the prin-
ter (On/Off Line). If the printer assumes an undefined state, the in-
terface also signals NOT READY and XOFF.
Memory mode Robust XON/
XOFF Robust XON/XOFF is similar to XON/XOFF. However, the state of
the printer (XON or XOFF) is also periodically transmitted via the
TxD line in the case of Robust XON/XOFF.