Commands: Controlling the Flow of Data
Data are ordinarily sent immediately from Pacterm to the TNC, and from the
TNC to Pacterm, but you may halt the flow of data in either direction.
Technical note: To avoid losing data, Pacterm and the TNC each need to know
when they have “permission” to send data to the other. Pacterm and the TNC
achieve this coordination using hardware flow control signals on the RS-232C ca
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ble connecting the two devices: (1) the TNC changes the status of the CTS (clear to
send) signal on one wire in the cable to tell Pacterm whether it is OK or NOT OK to
send it data, and (2) Pacterm changes the status of the RTS (request to send) signal
on another wire in the cable to tell the TNC whether it is OK or NOT OK for the
TNC to send data to Pacterm. The current status of each hardware control signal is
shown on the right end of the status line (RTS is shown if RTS is ON; CTS is shown if
CTS is ON)
F5 = Pacterm to TNC: Offline or Online (Default)
Pressing F5 (from either the MAIN Menu or the Terminal Screen) switches be-
tween two options controlling when data are sent from Pacterm to the TNC:
1. ONLINE = immediate transmission of data to the TNC as you enter it from
the computer (default setting), and
2. OFFLINE = type ahead, which orders Pacterm to stop the immediate trans
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mission of data and save the data in a transmission buffer, also called a
type-ahead buffer, for transmission to the TNC when you switch back ON
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LINE.
Caution: Don’t go OFFLINE for long. Pacterm’s type-ahead buffer (transmis
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sion buffer) holds a maximum of 1,024 characters, after which old data will be
discarded to make room for new data (i.e., it is a “first-in first-out” buffer)
The status line on the Terminal Screen shows either ONLIN or OFLIN.
Pacterm v 2.0 Commands: Controlling the Flow of Data
User’s Guide 84 KAM’98 v 8.3
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