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Device Control
ASCII TRANSFERS
Examples:
ESC
&
p 2s 2R Right tape unit is selected as the new
"from" device; send byte count before
sending next record
An ASCII transfer is specified by a read without byte
count. For reads without byte count (OR, lR, 4R) an enabl-
ing multicharacter transfer trigger (DCl) from your pro-
gram (following the escape sequence) causes one record to
be read and transmitted to the computer.
Send next record from the "from" device
ESC & p.OR
For reads without byte count (OR,IR), an enabling block
transfer from your program (following the escape se-
quence) causes one record to be read and transmitted to
the computer. A CR(LF)/RS/ GS terminator is appended to
the end of the record. Any Line Feed characters in a
record will not be transmitted if the.c::;;J
key is not
LF
latched down. When a file mark is read, the terminal
sends an RS (Record Separator) or GS (Group Separator)
followed by CR(LF). If the terminal is in BLOCK MODE
strapped for page, only RS or GS is sent. The escape
sequence must be repeated to read each record from a
device.
The read control byte has the following meanings:
o
=
Transmit next record with no byte count
1
=
Retransmit last record only
2 = Send byte count before transmitting next record
3
=
Send byte count before retransmitting last record read
4 = Transmit file
6
=
Transmit file with byte count before each record
indicated by a plus
(+)
or minus (-) sign preceding the
number. The tape is positioned before the first record of
the specified file (i.e., after the file mark of the previous
file). Files are numbered from 1 to 255.
DISPLAY
Unless the "skip p records immediately" function
(8)
is
used, an end-of-data mark will be written before a skip,
locate, rewind, or condition tape operation (0-4) is per-
formed, if the last function performed on the cartridge was
a record operation. "Skip p records immediately" inhibits
the writing of the end-of-data mark and is intended
primarily for write verification in a write-backspace-read
operation sequence. After using the "skip p records im-
mediately" function, a file mark must be written on the
tape before rewinding the tape. This function should not
be used to skip forward on a cartridge on which a record
function was the last operation.
Skip/locate functions (1,2,3, or
8)
are limited to the bounds
of load point and end-of-data (or end of tape). Any attempt
to exceed these bounds will cause the command to be
aborted, and the appropriate bits in the device status will
be set. To append a new file on a cartridge, first find the
end-of-data mark (3), then record a file mark (5) to termi-
nate the last file before starting a new file. If a file mark is
not written, the new data will be appended to the end of
the last file.
PRINTER
The display ignores all control functions. Any control
functions applied to the display will be flagged as execut-
ing successfully.
All functions, except the skip lines functions (1), cause one
ASCII Form Feed character (octal 14)
to
be sent to the
printer. The Form Feed character will cause some printers
to skip to the top of the next page. The skip lines function
will cause the printer to skip p lines using the absolute
value of p.
Generally, the terminator sent by the terminal in re-
sponse to the I/O control escape sequence may be a
CR(LF), RS, or GS depending on the communications pro-
tocol and terminal configuration (refer to section V).
Whenever the terminator is specified, the characters
CR(LF)/RS/GS will be used to denote the above conditions.
TRANSFERRING DATA FROM DEVICE TO
COMPUTER
If a byte count is specified in the escape sequence (2R, 3R,
or 5R), the information is sent in two steps.
STEP
1. When your program issues a block transfer
enable (following the escape sequence), the byte count
(the number of bytes in the record to be sent) will be
transmitted to the computer.
STEP 2.
When your program enables the next block
transfer from the terminal, the record will be sent to the
computer. All characters within the record will be sent
(including LFs). No record terminator will be appended to
the record. (After the record has been sent, the Request
to Send (CA) line from the terminal will be dropped for
about 5 milliseconds. This may be used as an interrupt
condition for the computer.)
Data may be transferred from the cartridge tape units or
display to the computer by the following escape sequence.
ESC & p
[< "from" device code> s]
[<read control byte>]r
BINARY TRANSFERS
The byte count is sent in binary as four bytes followed by a
CR(LF), or an RS/GS if the terminal is in BLOCK MODE,
strapped for page.
4-3
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