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SENDER RECEIVER
"s -k foo.bar"
"foo.bar open x.x minutes"
C
STX 01 FE Data[1024] CRC CRC
ACK
STX 02 FD Data[1024] CRC CRC
ACK
SOH 03 FC Data[128] CRC CRC
ACK
SOH 04 FB Data[100] CPMEOF[28] CRC CRC
ACK
EOT
ACK
Chapter 4 XMODEM Protocol Enhancements
X/YMODEM Protocol Reference 10-27-87 12
5. YMODEM Batch File Transmission
The YMODEM Batch protocol is an extension to the XMODEM/CRC protocol that
allows 0 or more files to be transmitted with a single command. (Zero
files may be sent if none of the requested files is accessible.) The
design approach of the YMODEM Batch protocol is to use the normal routines
for sending and receiving XMODEM blocks in a layered fashion similar to
packet switching methods.
Why was it necessary to design a new batch protocol when one already
existed in MODEM7?[1] The batch file mode used by MODEM7 is unsuitable
because it does not permit full pathnames, file length, file date, or
other attribute information to be transmitted. Such a restrictive design,
hastily implemented with only CP/M in mind, would not have permitted
extensions to current areas of personal computing such as Unix, DOS, and
object oriented systems. In addition, the MODEM7 batch file mode is
somewhat susceptible to transmission impairments.
As in the case of single a file transfer, the receiver initiates batch
file transmission by sending a "C" character (for CRC-16).
The sender opens the first file and sends block number 0 with the
following information.[2]
Only the pathname (file name) part is required for batch transfers.
To maintain upwards compatibility, all unused bytes in block 0 must be set
to null.
Pathname The pathname (conventionally, the file name) is sent as a null
terminated ASCII string. This is the filename format used by the
handle oriented MSDOS(TM) functions and C library fopen functions.
An assembly language example follows:
DB 'foo.bar',0
No spaces are included in the pathname. Normally only the file name
stem (no directory prefix) is transmitted unless the sender has
selected YAM's f option to send the full pathname. The source drive
(A:, B:, etc.) is not sent.
Filename Considerations:
__________
1. The MODEM7 batch protocol transmitted CP/M FCB bytes f1...f8 and
t1...t3 one character at a time. The receiver echoed these bytes as
received, one at a time.
2. Only the data part of the block is described here.
Chapter 5 XMODEM Protocol Enhancements
X/YMODEM Protocol Reference 10-27-87 13
+ File names are forced to lower case unless the sending system