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Unix programs supporting YMODEM are available on TeleGodzilla in RZSZ.ZOO.
This ZOO archive includes a ZCOMM/Pro-YAM/PowerCom script ZUPL.T to upload
a bootstrap program MINIRB.C, compile it, and then upload the rest of the
files using the compiled MINIRB. Most Unix like systems are supported,
including V7, Xenix, Sys III, 4.2 BSD, SYS V, Idris, Coherent, and
Regulus.
A version for VAX-VMS is available in VRBSB.SHQ.
Irv Hoff has added 1k blocks and basic YMODEM batch transfers to the KMD
and IMP series programs, which replace the XMODEM and MODEM7/MDM7xx series
respectively. Overlays are available for a wide variety of CP/M systems.
Questions about Professional-YAM communications software may be directed
to:
Chuck Forsberg
Omen Technology Inc
17505-V Sauvie Island Road
Portland Oregon 97231
VOICE: 503-621-3406 :VOICE
Modem: 503-621-3746 Speed: 19200(Telebit PEP),2400,1200,300
Usenet: ...!tektronix!reed!omen!caf
CompuServe: 70007,2304
GEnie: CAF
Unlike ZMODEM and Kermit, XMODEM and YMODEM place obstacles in the path of
a reliable high performance implementation, evidenced by poor reliability
under stress of the industry leaders' XMODEM and YMODEM programs. Omen
Technology provides consulting and other services to those wishing to
implement XMODEM, YMODEM, and ZMODEM with state of the art features and
reliability.
Chapter 11 Xmodem Protocol Overview
CONTENTS
1. TOWER OF BABEL................................................... 2
1.1 Definitions................................................. 2
2. YMODEM MINIMUM REQUIREMENTS...................................... 4
3. WHY YMODEM?...................................................... 5
3.1 Some Messages from the Pioneer.............................. 6
4. XMODEM PROTOCOL ENHANCEMENTS..................................... 9
4.1 Graceful Abort.............................................. 9
4.2 CRC-16 Option............................................... 9
4.3 XMODEM-1k 1024 Byte Block................................... 10
5. YMODEM Batch File Transmission................................... 12
5.1 KMD/IMP Exceptions to YMODEM................................ 16
6. YMODEM-g File Transmission....................................... 17
7. XMODEM PROTOCOL OVERVIEW......................................... 18
7.1 Definitions................................................. 18
7.2 Transmission Medium Level Protocol.......................... 18
7.3 File Level Protocol......................................... 19
7.4 Programming Tips............................................ 20
8. XMODEM/CRC Overview.............................................. 22
8.1 CRC Calculation............................................. 22
8.2 CRC File Level Protocol Changes............................. 23
8.3 Data Flow Examples with CRC Option.......................... 25
9. MORE INFORMATION................................................. 27
9.1 TeleGodzilla Bulletin Board................................. 27
9.2 Unix UUCP Access............................................ 27
10. REVISIONS........................................................ 27
11. YMODEM Programs.................................................. 28