Records - IBM 5100 Maintenance Information Manual

Records
Format Records
The format records are located on channel 0 of the
tape. The first 251 bytes of a record are hex 55; they
are used as a start/stop zone for the tape unit. The
next three bytes are used to provide position and timing
information to the controller. The first two of these
three bytes are hex 00; they are read, one bit at a time,
until the third byte, hex E7, is read.
~
Forward Tape Motion
Format
Record
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Format
Record
At this point, the tape unit and the processor are
synchronized, and the tape adapter switches to byte
mode.
The next byte is the record type; it indicates to the
controller whether the data track has a header record by
a data record written on it. Following this byte is the
record sequence byte; it identifies the riext record on
the data track. The next 29 bytes of hex 00 provide a
time delay that is used between erasing the data track
of one record and writing the data track of the next
record. The last four bytes of the format track are used
to establish synchronization and to determine the record
type if the tape unit is reading in. the reverse direction.
Format
Record
Last Data
I
........................
Header Record ............ Data Record Data Record
Number 2
Record in
Previous
File
No
Data
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251 Bytes of Hex 55
.................. Number 1
............
................
R ecor dT ype
....................................
~ I~ I~
I ' I I
29 Bytes of Hex 00
' - , , - ' .
Record Sequence Number
............
......
E 0
7 0
.......
-
0
0
I
No
Data
r-----
Record Type) - - - - -....
Format Record
) Record Type:
4-34
Header - Hex 81
Data - Hex 18
o
0
No
7 0 0 Data
File Number Number of Bytes Allocated to File
Hex 0001·7FFF - -....
1
r -
Hex 0001·3FFF
.--"'--...
--..
Language Dependent Information
File Type
/