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READY/BUSY FLOW CONTROL
Ready/Busy is the hardware flow control method for the serial interface on the CT
printers. By raising/lowering the voltage level on Pin 20 of the RS232 port, the
printer notifies the host when it is ready to receive data. Pin 4 (RTS) and pin 20
(DTR) are the important signals on the printer for this method of flow control. The
DB9 DB25 HOST INTERCONNECTION PRINTER
11FG
←→
1 FG (Frame Ground)
23RD
← 2. TD (Transmit Data)
32TD
→
3 RD (Receive Data)
85CTS
← 4 RTS (Request to Send)
74RTS
→ 5 CTS (Clear to Send)
420DTR
→ 6 DSR (Data Set Ready)
6 6 DSR*
←
20 DTR (Data Terminal Ready)
57SG
←→
7 SG (Signal Ground)
* This connection at the host side of the interface would depend upon the pin that is being used as the Ready/Busy signal by the
driving software. Typically, on a PC, it would be either CTS (pin 5) or DSR (pin 6) on a DB-25 connector.
PIN DIRECTION SIGNAL DEFINITION
1 Reference FG (Frame Ground)
2 To Host TD (Transmit Data) - Data from the printer to the host computer.
Sends X-On/X-Off characters or status data (Bi-Directional
protocols).
3 To Printer RD (Receive Data) - Data to the printer from the host computer.
4 To Host RTS (Request to Send) - Used with Ready/Busy flow control to
indicate an error condition. RTS is high and remains high unless
the print head is open (in this case, RTS would return to the high
state after the print head is closed and the printer is placed back
on-line) or an error condition occurs during printing (e.g., ribbon
out, label out).
5 To Printer CTS (Clear to Send) - When this line is high, the printer assumes
that data is ready to be transmitted. The printer will not receive
data when this line is low. If this line is not being used, it should be
tied high (to pin 4).
6 To Printer DSR (Data Set Ready) - When this line is high, the printer will be
ready to receive data. This line must be high before data is
transmitted. If this line is not being used, it should be tied high (to
pin 20).
7 Reference SG (Signal Ground)
20 To Host DTR (Data Terminal Ready) - This signal applies to Ready/Busy
flow control. The printer is ready to receive data when this pin is
high. It goes low when the printer is off-line, either manually or due
to an error condition, and while printing in the Single Job Buffer
mode. It will also go low when the data in the buffer reaches the
Buffer Near Full level.
RS232C Interface Signals
Section 5. Interface Specifications
Page5-69001069A SATOCTSeriesPrinters