Interfaces User guide164ENQ/STX protocol In addition to this XON/XOFF message, the possibility exists of re-questing a status byte from the printer using the ENQ code (hex. 05,dec. 5). The STX code (hex 02, dec. 2) is used to clear any errormessages (parity error, buffer overflow).STX (hex02) Clears any previous parity or framing error as wellas any buffer overflow error.ENQ (hex05) The current printer status is sent to the host.XON/XOFF This protocol is automatically used for data flowcontrol and printer status handling.HandThr.=ON The STX and ENQ characters are not filtered outof the data stream and control the interface in ad-dition.HandThr.=OFF The STX and ENQ are filtered out of the data st-ream and handled immediately by the interface.ETX/ACK protocol ETX (hex03) Block end characterACK (hex06) Acknowledgement informing the host that furtherdata may be transmitted.XON/XOFF This protocol is used in addition to data flow con-trol and printer status handling.HandThr.=ON An ETX is not acknowledged by ACK before allpreviously arrived data have been printed.HandThr.=OFF When the printer receives an ETX, it returns anACK to the host. Any previously sent data orblocks may still be present in the printer buffer.Status byte Bit 0 – 1 BUSYBit 1 – 1 Off LineBit 2 – 0 Paper endBit 3 – 1 Always 1Bit 4 – 1 Cover openBit 5 – 1 Buffer overflowBit 6 – 1 Parity or frame errorBit 7 – 0 Always 0
