POSIFLEX Business Machines PP3000 - Manual (Page 36)

Framing error
A framing error occurs when “SPACE” is detected at the stop bit. When a
framing error or a vertical parity error occurs for the data which is received, the
printer prints out a “?” mark to indicate that the error occurred.
Cash drawer open detection switch
When pin 6 of the peripheral unit drive circuit connector is set at
“HIGH”, status bit 7 becomes “1”.
STX-ETX Mode
This mode is accessed from whichever DTR mode or X-ON/X-OFF
mode. To set this mode, the data buffer must be empty. The host computer sends
an “ENQ” code to the printer and acknowledges the printer status. Then, the host
computer checks if the printer buffer is empty. After the host computer detects
that the buffer is empty, a STX code and data are transmitted. After 1 block of
data is transmitted, the host computer sends an ENQ code to the printer and then
receives the printer status and check byte (horizontal parity for the printer). At
this point, the host computer performs a status and horizontal parity check.
When the host computer determines that there was no error, it transmits an ETX
code which serves as end text code. After the printer receives the ETX code,
data in the data buffer is printed out. If an error occurs, a CAN code is
transmitted by the host computer (In this instance, the data which was
previously sent to the buffer is cleared, thus, the host computer must retransmit
the same data to the printer). A flowchart of this operation is illustrated as the
following on next page.
PP3000 Series User’s Manual 4 - 12