xprDModem V2.1 - User/Tech 'manual' Copyright 1992-1994 By Pasi Ristioja, all rights reserved. (This is giftware release, read license.boring) Mailing address Pasi Ristioja Urpiaistie 8 96400 Rovaniemi Finland Bugreports FIDO: 2:229/888 (Pasi Ristioja) INTERNET: pasi.ristioja@mpoli.fi Introduction/Use ~~~~~~~~~~~~~~~~~~ One way transfer should work with any xpr aware commprog if option XN is used, birectional transfer will need commprog to understand unofficial xpr2.001. Remember that this protocol is aimed to use only with error correcting modems (v42/mnp). Of course you can use dmodem without that kind of modem but I strongly recommend not to. This not mean that error detecting isn't secure. It's only that protocol isn't designed to handle multiple errors efficiently. There is major speedup when using DreamTerm 1.x with DModem, this is achieved using internal double buffering in xprdmodem. This technique offers possibility handle RXD while TXD is still running, this is very important when doing bidirectional transfer. (This was the main reason why I was forced to upgrade xpr2.0.) Example: (For tech freaks) 1. Dmodem sends 2048 byte block (a) / xpr_swrite - DTerm starts to send it and returns immediately. 2. Dmodem sends 2048 byte block (b) / xpr_swrite - DTerm checks if a-block is sent already, if not it waits send to complete. (To modem) 3. Dmodem sends 2048 byte block (c) / xpr_swrite - same as 2 Note: There is no more chatmode -> I'll may add it later. DModem options ~~~~~~~~~~~~~~~~ biup yes/no (i) - default is no. (IN) yes (IY) - Uploader waits receiver(user) to start upload. Only BBS should use this! When user wants to make bidirectional transfer she/he first chooses what to dnload and then starts to upload. Same time BBS starts uploading BUT waits 60 seconds before starts actual upload. This means that user has 60 seconds to choose which files to send. (Without this option autoupload is impossible!) no (IN) block [] (b) - default is 2048. (B2048) Blocksize, legal range is 256 - 8192. Keep in mind that memory usage is about blocksize*9. Do not set this much lower than your linkspeed, it may cause error correcting to give up more easily. (BBS should set this to 8192 if possible) dpath (d) - default is current directory. (D) Download path (Generally no use). upath (u) - default is current directory. (U) Upload path (Generally no use). enablexpr2.001 yes/no (x) - default is no. (XN) yes (XY) - Dmodem will use xpr2.001 specs, bidirectional xfer is available only with this. no (XN) - Dmodem will use xpr2.0 specs, with this any commprog which support xpr should be able to use dmodem but bidirectional xfer is impossible. lowcpu yes/no (l) - default is yes. (LY) yes (LY) - Dmodem will try to go idle and let other tasks use cpu. Only problem is that this somehow depends how commprog is implemented its xpr-driver, this can cause lower upload performance when doing bidirectional transfer. no (LY) - Dmodem steals all available cpu. Notes ~~~~~~~~ When I designed this protocol I was forced to upgrade xpr2.0 specs in order to gain maximum performance, read xprprotocol.doc if you want to learn about modifications. If you use terminal program which doesn't understand xpr2.001 specs you must use option XN. Problems ~~~~~~~~~~ A500 : Bidirectional transfer is almost too much for this old machine, do not use greater DTE than 19200 if you want error free transfers. Also reducing screen colors to 2 or 4 will help. HardDrive: Old drives (like supra) will cause serial overruns when writing to disk. If this is the case you must use RAM: as download directory. Misc ~~~~~~ This version will not work with 1.0ß - 2.0, do not use them. CRC routine is © Kimmo Mustonen, thanks. Performance ~~~~~~~~~~~~~ Estimations about packed data cps (Multiple by 2 to get combined cps) --------+-------------+------+------+------+ Filesize| Effiency | V32 | V32b | Zyx16| --------+-------------+------+------+------+ 2048 | 99.32 | 1093 | 1688 | 2034 | 4096 | 99.59 | 1095 | 1693 | 2040 | 8192 | 99.72 | 1097 | 1695 | 2042 | 16384 | 99.79 | 1098 | 1696 | 2044 | 32768 | 99.82 | 1098 | 1697 | 2044 | 65536 | 99.84 | 1098 | 1697 | 2045 | 131072 | 99.85 | 1098 | 1697 | 2045 | --------+-------------+------+------+------+ 2196 3394 4095 Combined best - Blocksize 2048, 11 bytes long filename - Calculations do not include protocol sync (start) Note: DModem do not acknowledge received files and due that real performance gain against ZedZap etc. is even higher than chart shows.