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DeB Start I/O Examples
Following are six examples detailing the use of the device
dependent bits contained in the DCB Control Word and
Device Parameter 4.
Example 1
lxample 2
START (Read From Buffer) Input
START (Set Cursor and Device States)
Output
lxample 3
Example 4
START (Write to Buffer/Protected) Output
START (Write/Erase-After to End of Line)
Output
Example 5
ST AR T (Shift Lines/Write Protected/Erase
After) Ou tpu t
lxample 6
START (Erase Unprotected) Output
START (Read From Buffer) Input
Device Parameter 4
Control Word
Bits
0
N/A
Off
Bits
8
Erase-After
Off
1
P/U
Off
9
EOF
Off
2
Kyb-Lo
Off
10
EOL
Off
3
Blank
Off
11
Erase
Off
4-10
N/A
Off
12
Post-Cursor
On
11-15
Shift Count
Off
13
Pre-Cursor
On
14
U/D
Off
15
Shift
Off
Byte Count
=
XXXX (Hex) as required
This command moves the cursor to the position designated
by Device Parameter 2 on the display screen and reads the
data character from the display refresh buffer designated
for that position. If the character is a NULL character a
Hex 00 will be sent to processor storage.
If
the data
character is not a NULL character, the EBCDIC character, if
unprotected, will be sent to processor storage. Only
unprotected characters are stored in contiguous processor
storage; protected characters are skipped over and not
transferred to processor storage. The Byte Count is
decremented for each unprotected character (byte count is
not decremented when protected characters are skipped
over), including NULLs. Subsequently, the cursor is
incremented one character position to the right and this
routine is repeated until the Byte Count reaches zero.
At the completion of the data transfer, the cursor is
moved to the position designated by Device Parameter 1 on
the display screen. The 80th data character position of
each line wraps to the first character position of the next
lower line during the operation.
Appendix B. Start 110 Examples
If
an EOS condition is detected prior to the Byte Count
reaching zero, an Exception Interrupt occurs. The keyboard
is unlocked (enabled), and the display screen isunblanked
at the completion of the data transfer.
STAR T (Set Cursor and Device Status) Output
Device Parameter 4
Control Word
Bits
0
N/A
Off
Bits
8
Erase-After
1
P/U
Off
9
EOF
2
Kyb-Lo
On
10
EOL
3
Blank
On
11
Erase
4-10
N/A
Off
12
Post-Cursor
11-15
Shift
Off
13
Pre-Cursor
14
U/D
15
Shift
Byte Count
=
0000 (Hex)
This command cycle steals only the DCB from processor
storage. The cursor is moved to the post-cursor position
Off
Off
Off
Off
On
Off
Off
Off
as designated by Device Parameter 2, the keyboard is locked
out (disabled), and the display screen blanked at the
completion of the command.
START (Write to Buffer/Protected) Output
Device Parameter 4
Control Word
Bits
0
N/A
Off
Bits
8
Erase-After
Off
1
P/U
On
9
EOF
Off
2
Kyb-Lo
Off
10
EOL
Off
3
Blank
Off
11
Erase
Off
4-10
N/A
Off
12
Post-Cursor
Off
11-15
Shift Count
Off
13
Pre-Cursor
On
14
U/D
Off
15
Shift
Off
Byte Count
=
XXX (Hex) as required
This command moves the cursor to the pre-cursor position
on the screen, and reads data characters from processor
storage. All of the EBCDIC" characters are marked protected,
except NULL (Hex 00) characters, and are subsequently
written into the display refresh buffer designated for that
cursor position. A protected character cannot be altered
by the local user via the keyboard.
If the data is a NULL character, an unprotected NULL
character is written at that position, and the cursor is
incremented one position to the right until the Byte Count
reaches zero. At the end of the previous operation, the
cursor is repositioned at the last previous cursor position
prior to the output operation.
Note.
Incorrect EBCDIC characters are translated to NULL
codes and entered into the display buffer as Hex-OO.
Start I/O Examples
B-1
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