One special thing ASCII like ZMODEM is the need for flow control. While standard 2400, 1200 or 300 baud users can ignore this, all other users must pay attention to it. Compression and error control schemes like MNP, PEP, and HST cause the normal maximum speed of the modem to be lower than what it actually is (i.e. a 2400 MNP connection might actually be going around 2200 baud). But telecommunications programs can only feed and read from the modem at the exact connect speed. All modems that support some kind of compression or error control also support internal flow control. In summary three things must be true to use Z-Modem correctly:
1) You must be using a properly wired modem cable. (See your modem’s or communication program’s manual)
2) You must have a communications program that supports flow control and have it turned on. (See your communication program’s maual)
3) You must have the modem’s registers set so that it will use the kind of flow control you are using in your communications program. (See your modem’s manual)
With these settings, you should be getting near maximum speed on most connections. 2400 baud callers should be getting about 96% efficiency, and Telebit PEP connections should get about 1400-1600 cps. If you aren't seeing these speeds, it is probably a flow control problem.
People on the terminal side might get away with no flow control for downloads, but it is an absolute must for uploading when using error correcting modems!
~SB~Problems:~SB~
If you have a question about this ASCII PROC you can find me (John Raymonds) at: 76174,205 on Compuserve and D3885 on AppleLink.
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This “protocolless” protocol is provided with its source code and is to be used as an example for writing more complex (and useful) protocols.
• 052990 - ~SB~Version 1.0d6~SB~ A sample preferences dialog has been added to set the creator of the ‘TEXT’ file. e
