SECTION 5
Communications and Device Support
PEN*KEY
R
6200/6300 Hand-Held Computer Programmer’s Reference Guide 5-5
TCOM Session Overview
Under the NORAND standard file transfer session, the HHC always uploads
first. Once all upload files are sent, the line is turned around and the host then
sends any download files. Each file is preceded by a header record that gives the
receiving computer information about the format used by the file.
The HHC must first send a session control file, which identifies the HHC to the
host computer. The HHC may then send a download request file. This optional
file prepares the host computer to download one or more files to the HHC.
Upload files can then be sent to the host.
Session Control File
To identify itself to the host, the HHC sends the session control file at the
beginning of a TCOM session. The applicationĆdependent HHC ID is used by the
host to determine which files to downloading to the HHC. The format of the
session control file is as follows:
<DSCNTRL00001Xnnn>PPPPPPPPPPPPPPTTTTTTTTTTTTTTTTYYMMDDHHMMSS . . .
where:
< = beginning of file header
D = file type (fixed)
SCNTRL = file name (fixed)
00001 = decimal number of records in file (fixed)
X = data type (ignored by host)
nnn = decimal number of bytes in file record
> = end of file header
PPPPPPPPPPPPPP = program identification
TTTTTTTTTTTTTTTT = hand-held computer ID (determined by application)
YYMMDD = date
HHMMSS = time
. . . = additional HHC information
The application determines the actual data in the session control file. The data
fields shown in the preceding list represent a convention used in applications
from Intermec Technologies Corporation. However, the session control header
always consists of 18 bytes. Also, NORAND host communication packages
usually expect to find the HHC ID starting in byte 33 of the data stream.
Although, this location is configurable.
Download Request File
An HHC may directly request specific files from the host. To do this, it sends a
download request file to the host immediately after sending the session control
file. The requested files are not downloaded at that moment, but rather after
the line is turned around.
If a download request file is sent, the host does
not
use the HHC ID in the
session control file to determine which files to download to the HHC. Only files
requested in the download request file are downloaded.
"
NOTE:
The download request file must be the first or second file sent. Otherwise, it is not treated as
a special file by the host.
5. Communications
and Device Support
