Monitor Mode; Configuration - HP 2641A Reference Manual

Data Communications
MAIN CHANNEL (CHARACTER CONTROL) PRO-
TOCOL. The Main Channel protocol is for use in half-
duplex or Bell 202 modem equivalent networks where
secondary channel signals are not available. The Main
Channel protocol uses control characters to "frame" each
data transmission. These framing characters indicate to
the receiving station that a data transmission has begun
or ended.
The following settings should be made on the Keyboard
Interface PCA to operate using the Reverse Channel
protocol.
SWITCH SETTING DESCRIPTION
R Closed Monitor the CB line
Closed, Closed Reverse Channel (no
framing characters)
An ASCII STX (octal 002) character can be used to indi-
cate the start of a data transmission. An ASCII ETX (octal
003) or EOT (octal 004) character is used to indicate the
end of a data transmission. When these characters are
received they are used to perform a line turn-around.
The following switch settings should be made on the
Keyboard Interface PCA to operate using the Main Chan-
nel protocol:
S,T
U
V
Closed
Closed
Watch for computer inter-
rupts (SB>O)
Watch for Carrier (CF)
transitions
SWITCH
R
S,T
SETI'ING
Open
Closed, Open
Open, Closed
Open, Open
DESCRIPTION
<STX> data <ETX>
data <EOT>
data <ETX>
Example:
W,X,Y,Z All Open - Variations of the Reverse
Channel protocol are discussed under Other Protocols and
in Appendix C.
The operation of the Reverse Channel protocol is shown in
figure 5-8. Sample data transfers are shown in figure 5-9.
Note that at least one of the S or T switches must be open
to select Main Channel protocol.
E;cample:
U,V,W,X,Y,Z All Open - Variations of the Main
Channel Protocol are discussed under Other Protocols and
in Appendix C.
The operation of the Main Channel protocol is shown in
figure 5-6. Sample data transfers are shown in figure 5-7.
Figures 5-7a and 5-7b illustrate the line turn-arounds that
occur during a log-on sequence when in character mode.
Figures 5-7c and 5-7d illustrate the transfers that occur
during block mode operation.
REVERSE CHANNEL (SIGNAL LINE CONTROL)
PROTOCOL. The Reverse Channel protocol is for use
in half-duplex or Bell 202 modem equivalent networks
where secondary channel signals are available. The Re-
verse Channel protocol uses changes on secondary channel
lines SA (CCITT 120) and SB (CCITT 122) to control line
turn-arounds.
5-16
OTHER PROTOCOLS. In addition to the Main and
Reverse Channel protocols you can select various features
of both to configure a custom protocol to suit your own
requirements. A flowchart of the overall Basic Communi-
cations function including the Half-Duplex settings is
given in Appendix C. You can create a custom protocol
using this flowchart and the switch descriptions in table
5-8. When more than one terminal must share a modem or
hardwired communication line, the Multipoint protocol
must be used. Refer to the description of Block Protocols.
MONITOR MODE
Monitor Mode is an added feature available with the
13260A and 13260B interfaces. Refer to Multipoint
Monitor Mode for a description.
CONFIGURATION
A procedure for configuring the terminal for point-to-point
operation is given in 10.