Raymar Alliance V.32, Инструкция по эксплуатации

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0049-2702-XXX Alliance Series Modems – USER MANUAL 08/05/2010
Rev. A Page 39 of 197
DTE speed refers to the speed of data transfer between the DTE and the local modem –
it is
not necessarily the same as the data transmission speed between the connected modems.
If flow control is disabled, the DTE speed must be equal to or less than the modem speed, and
the local and remote DTE speeds must be equal.
For Hayes mode operation, this option sets the default DTE speed that will be effective after
powerup or after a full modem reset. However, the default DTE speed is automatically
overridden when the ALX is autobauded (when and “AT” attention code is sent to the ALX.)
Flow Control
The flow control options control the data flow according to the availability of memory “space”
in the buffer. Flow control can be set independently for the terminal to the modem (DTE-
DCE) and for the modem to the terminal (DCE-DTE). The flow control options include DTE-
DCE, DCE-DTE and Pass-through Flow Control. Two additional flow control options are
described later in this chapter.
Note the following:
•
Flow control only applies to asynchronous connections with V.42 error correction or
Buffer Mode enabled.
•
When flow control is disabled, the DTE data rate must be equal to or less than the
modem data rate, and the local and remote DTE data rates must be equal.
(This
precludes the need for flow control – which some DTE devices cannot handle – and
avoids buffer overflow.)
•
For DTE-DCE and DCE-DTE Flow Control options: When RTS or CTS flow control
is used and a buffer connection has been established, conditions that will stop the data
flow (e.g., dropped RTS) should not be permitted for long periods, if possible, to
reduce the possibility of buffer overflow.
Figure 2-1 illustrates the available flow control options.