res@colnet.uucp (Rob Stampfli) (03/12/91)
I own an Intel 9600ex modem. The instructions are not too clear about the following commands, which deal with reliable mode. Could someone expand on what the following commands do: 1. AT\O -- originate reliable link 2. AT\U -- accept reliable link 3. AT\Y -- switch to reliable mode 4. AT\Z -- switch to normal mode These are purported to be used after the connection is initially established. I could understand AT\Y and AT\Z if there were no AT\O or AT\U, but obviously there is something I don't understand. Also, the 9600ex gives three options for dealing with how the modem handshakes to establish a reliable connection. These are: 1. AT\C0 -- If a reliable connection is made, no buffering occurs, and the fallback character detection is disabled. (Default) 2. AT\C1 -- The modem buffers data until either 200 normal characters are received or a reliable character is received within three seconds of making a connection. If the modem receives 200 normal characters, it makes a normal connection (no error control). No buffering occurs and the modem passes data to the computer as soon as the modem receives the data. If the modem receives a reliable character, it initiates a reliable connection, and the fallback character detection is disabled. 3. AT\C2 -- If a reliable connection is made, no buffering occurs. If the modem detects the fallback character, it falls back to normal mode. Which method is most commonly used? What is a "reliable character"? Thanks in advance, -- Rob Stampfli, 614-864-9377, res@kd8wk.uucp (osu-cis!kd8wk!res), kd8wk@n8jyv.oh
news@armon.rain.com (Mehdi Attaran) (03/15/91)
In article <1991Mar12.034943.10592@colnet.uucp> res@colnet.uucp (Rob Stampfli) writes: >I own an Intel 9600ex modem. The instructions are not too clear about the >following commands, which deal with reliable mode. Could someone expand on >what the following commands do: > >1. AT\O -- originate reliable link >2. AT\U -- accept reliable link >3. AT\Y -- switch to reliable mode >4. AT\Z -- switch to normal mode > >These are purported to be used after the connection is initially established. >I could understand AT\Y and AT\Z if there were no AT\O or AT\U, but obviously >there is something I don't understand. > >Also, the 9600ex gives three options for dealing with how the modem handshakes >to establish a reliable connection. These are: > >1. AT\C0 -- If a reliable connection is made, no buffering occurs, and > the fallback character detection is disabled. (Default) >2. AT\C1 -- The modem buffers data until either 200 normal characters > are received or a reliable character is received within three > seconds of making a connection. If the modem receives 200 > normal characters, it makes a normal connection (no error > control). No buffering occurs and the modem passes data to > the computer as soon as the modem receives the data. If the > modem receives a reliable character, it initiates a reliable > connection, and the fallback character detection is disabled. >3. AT\C2 -- If a reliable connection is made, no buffering occurs. If > the modem detects the fallback character, it falls back to > normal mode. > >Which method is most commonly used? What is a "reliable character"? First I must say that ALL of the commands mentioned in your message are MNP related. They do not affect the LAPM (V42) connections. With that in mind, I'll try to explain each command: \O and \U commands work together. They are useful for negotiating a MNP connection, when a normal connection is already stablished. Here's how they work: - put both modem is command mode (+++) - Issues the AT\U command to one modem. This assures that the modem is ready to accept a MNP (reliable) connection. - You then have exactly 12 seconds to issue an AT\O command on the othe modem. This will put the modem in originate-reliable mode, and the modem will re-negotiate for a MNP connection. The MNP negotiation is performed by sending ASCII characters to the remote unit. These ASCII characters are called "reliable characters". A "fallback character" is sent to the remote modem, to force a switch from MNP (reliable) mode to normal (non-reliable) mode. The originator of a MNP connection can issue the \Z command to send a fallback character to the remote unit. This will force fallback from a MNP connection to a normal connection. The \C command controls the behavior of the 200 character buffer the modem has when it's attempting a handshake. The various setting are as follows: \C0: The 9600EX does not buffer any character comming from the remote modem as it's negotiating for a MNP connection. 9600EX DOES NOT check wether a fallback character has been received. (i.e. 9600EX ignores the fallback character received from a remote modem.) \C1: As the 9600EX is negotiating for a MNP connection, it buffers up to 200 character received from the remote modem during this handshake. If a MNP connection is not made (i.e. the 9600EX received 200 normal characters, no reliable characters were received) the 9600EX will pass the buffered characters to the computer. \C2: If a MNP connection is negotiated, the buffer is purged. 9600EX does recognize the fallback character in this setting. Although the factory default is \C0, I am using the \C1 setting as it makes it easier to logon to non-MNP capable systems. -- ..!uunet!m2xenix!armon!news news@armon.rain.com (Mehdi Attaran)