Module
4 - Modems: Setup and Diagnostics
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Configuring Modem Software
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Set speed to 4X maximum modem speed and compression
ratio (4:1)
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Number of data bits, parity and stop/start bits
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Handshaking is usually hardware (RTS/CTS) not
software (XON/XOFF)
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Universal Asynchronous Receiver/Transmitter
(UART) Chips
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Processes both incoming and outgoing serial
data
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Win 95/98 identifies the type of UART chip installed
16550
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Converts the parallel data into a serialstream
and adds parity
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Trouble Shooting pg 284
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Self-diagnostic routines are run
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Loopback tests are performed for self-diagnostics
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Analog tests test the internal circuitry of
the local modem
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AT&T0 or ATU or ATU0
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typed data should return
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+++AT and then AT&T0
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Digital tests test the entire system.
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Local requires the remote modem to send and
receive
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Remote is the reverse with local sending and
receiving
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AT Command Set
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Modem Commands (table pg 286)
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Hayes is the standard for modem connection
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AT command language all commands start with
AT
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A - answer, D - dial, H - Hangup, Z - reset
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S registers (programmable registers)
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0 - number of rings (ATS0=3 would answer on
the third ring)
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7 - number of seconds to wait after dialing
(ATS7=45 would wait 45 secs)
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Modem commands can be strung together