User guide Interfaces126ProtocolsMemory 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 128 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 resultsin stopping the data transmission. When the FIFO buffer is emptyagain, 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/XOFFRobust XON/XOFF is similar to XON/XOFF. However, the state ofthe printer (XON or XOFF) is also periodically transmitted via theTxD line in the case of Robust XON/XOFF.
