Epson PX-8 User Manual page 93

When data is read from the tape if Stop mode is set the tape again stops be-
tween each block of data before the next block is read. If Non-Stop mode is
set, the data is read consecutively. Unless otherwise set, the data is read in the
same mode it was written in.
<READ>
256 bytes each
T T T T
Block2 Block3
EOF
Seek
.. Stop in Stop mode
Fig. 4.9
'" Stop in Non-stop mode
In reading and writing files using the STOP mode this has the following effects:
i)
More tape is used when the Stop mode is used to write a file.
ii)
The file takes longer to write.
iii) When reading a tape written in the Stop mode, more accurate reading
is possible.
iv) In extreme cases errors can occur in reading files written in Non-Stop
mode. This is most likely to happen when reading single records from a
file as this requires the Microcassette drive to be stopped and started by
the program. When the tape stops under program control it cannot al-
ways stop in the correct position in front of the next record. Thus it can
miss the record or part of it and generate an error. This can be overcome
by reading the record in Stop mode. As further security against this errOl:
occurring read and write such files in Stop mode, by setting the STOP
mode from the System Display before running the program.
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j)
The Verify and Non-Verify Mode
In order to ensure accurate recording of data on a Microcassette tape, it is pos-
sible to have the data checked by specifying the Verify mode when the data
is written. The Verify mode is switched on and off from the System Display,
(see section 2.2.3.e).
In the verify mode, each 256-byte block is verified after the entire file has been
written to the tape.
If an error is detected, one of the following messages is displayed.
BDOS ERROR ON H: BAD SECTOR
Disk Read error
(under CP/M)
(under BASIC)
In the Non-verify mode, files written to tape are not verified.
It
is recommended that the verify mode be used when writing files to cassette
tape.
When a file is written, the Microcassette drive will carry out the following
procedure:
i) The tape will be wound to the next available position. Sometimes it may
rewind to the beginning of the tape and then wind on so that it can be
sure to be at the correct position.
ii) The REC light will come on and the file will then be written to the tape.
The tape may stop and start if the Stop mode is set.
iii) The REC light will go out.
iv) If Verify is set, the tape will be rewound to the start of the file and the
file will be checked.
v) The tape will stop and the EJECT button will be unlocked.
Verify does not operate when reading tapes.
k) Rules for day to day use of the Microcassette Drive.
1) Always check that a tape has been REMOVEd before taking it out of the
drive, otherwise the directory will not be written back to the tape, and could
be written to another tape.
2) Never use DIRINIT without checking the directory of a tape if it is not a
new one.
3) Never switch off while a file is being recorded or read. The file will not be
appear on the directory if the power is switched off manually while record-
ing is taking place.
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