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CHAPTER 7: Configuring DTE Options
7.4 DTE Command Option
The DTE Command option is used to enable a DTE command mode or disable
all modes. The available modes are AT, V.25 synchronous, and V.25
bisynchronous/asynchronous commands.
7.5 Transmit Clock
The Transmit clock option is used to select the source of the clock used to transfer
data from the DTE into the CSU/DSU MS DBU. Table 7-1 shows the AT
commands used to set the Transmit Clock options.
The External clock option is normally used in modem tail-circuit applications.
A DSU-to-modem interconnect diagram for this application is shown in Appendix
E. The External clock option is also recommended when the EIA-232 connector
is used for 56-kbps and 64-kbps applications. Using this option eliminates data
errors caused by excessive delays in the DTE transmit clock receiver and
transmit data driver.
The Invert clock option is recommended when the EIA-232 connector
is used for rates other than 56 kbps or 64 kbps.
7.6 Clear to Send (CS) Options
The CS Options menu is used to select the control mode for the CS lead.
The default factory setting is Follows RS with CS Delay Short.
If one of the options chosen involves request to send (RS), then the delay from
RS to CS must be selected. Table 7-1 shows the AT Commands used to set the
CS options.
Specified times for the short and long delays at the different operating speeds are
shown in Table 7-2.
Table 7-2. Short and Long Delays at Different Operating Speeds
Rate
Short Delay
Long Delay
64 ...................1.1 ms ................16.1 ms
56 ...................1.1 ms ................16.1 ms
19.2 ................1.5 ms ................16.5 ms
4.8 ................1.5 ms ................16.5 ms
2.4 ................1.5 ms ................16.5 ms