Module 4 - Modems: Setup and Diagnostics

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