Ready/Busy Flow Control - SATO LC400e Series Operator's Manual

7.2 RS-232C HIGH SPEED SERIAL INTERFACE (Cont'd)
Note
Some hosts monitor the Request-To-Send (RTS) signal (pin 4 of 25) to determine if the printer is ready
to receive data. Since the printer does not generate this signal, the RTS line must be held true (high) in
order to allow communication. This can be performed by connecting the RTS pin to the Clear-To-Send
(CTS) signal (pin 5 of 25).

7.2.3 READY/BUSY Flow Control

Pin Assignments
PIN DIRECTION
1 Reference
2 To host
3 To printer
4 To host
5 To printer
6 To printer
7 Reference
20 To host
LC400e Series Operator Manual
13
25
Figure 7-1, Serial Connector Pin Assignments
READY/BUSY INTERFACE SIGNALS
FG (Frame Ground)
TD (Transmit Data) - Data from the printer to the host computer. Sends X-On/X-Off
characters or status data (bi-directional protocols).
RD (Receive Data) - Data to the printer from the host computer.
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 online) or an
error condition occurs during printing (for example, label out).
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 the line is low. If this line is not being
used, it should be tied high (to pin 4).
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).
SG (Signal Ground)
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 offline, 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.
Section 7: Interface Specifications
14
SIGNAL DEFINITION
1
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