POSIFLEX Business Machines PP3000 manual STX-ETX Mode

TM

CHAP. 4

TECHN…

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.

4 - 12