Printek PrintMaster 700 Series, Руководство пользователя

Страница: 112 / 126

103
͎
ENQ/STX protocol
In addition to this XON/XOFF message, the possibility exists of requesting 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 error messages (parity error, buffer overflow).
Status byte Bit 0-1
BUSY
Bit 1-1
Off Line
Bit 2-0
Paper end
Bit 3-1
Always 1
Bit 4-1
Cover open
Bit 5-1
Buffer overflow
Bit 6-1
Parity or frame error
Bit 7-0
Always 0
STX (hex02):
ENQ (hex05):
XON/XOF:
HandThr.= ON:
HandThr.= OFF:
Clears any previous parity or framing error as well as any buffer overflow
error.
The current printer status is sent to the host.
This protocol is automatically used for data flow control and printer status
handling.
The STX and ENQ characters are not filtered out of the data stream and
control the interface in addition.
The STX and ENQ are filtered out of the data stream and handled
immediately by the interface.
͎
ETX/ACK protocol
ETX (hex03):
XON/XOFF:
ACK (hex06):
HandThr.=ON:
HandThr. =OFF:
Acknowledgement informing the host that further data may be transmitted.
This protocol is used in addition to data flow control and printer status
handling.
Block end character.
An ETX is not acknowledged by ACK before all previously arrived data have
been printed.
When the printer receives an ETX, it returns an ACK to the host. Any
previously sent data or blocks may still be present in the printer buffer.
͎
ACK/NAK protocol
The ACK/NAK Protocol is a so called block Protocol.
Normally the Blocks are starting with the Block Start Character (STX, dec 02, hex 02) and end
with a Block End Character (ETX, dec 03, hex 03).
As soon as a Block is received by the printer it acknowledges it with the Acknowledge
Character (ACK, dec 06, hex 06).
If there is an Error in the transmission a Not-Acknowledge-Character (NAK, dec 21, hex 15) is
being sent back. As a block end character other codes are possible.
One can check the printer condition/status; During the transmission of graphic data or
download character per se problems can come up within the block mode as in this data block
end characters can be transmitted as normal graphic or other data.