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Write Command
The Write command writes data into specified locations in the 3708 buffer without
erasing or modifying data in the other locations. Data is stored in successive buffer
locations until an order is encountered in the data stream that alters the buffer
address, or until all the data has been stored. During the write operation, the buffer
address is advanced one location as each character is stored.
The buffer location where the entry of data starts depends on the starting location
specified by the Set Buffer Address order (see "Set Buffer Address (SBA)" on
page 4·11) that follows the WCC. If an SBA does not follow the WCC, the starting
location is the buffer address where the cursor is positioned. The formatting and
placement of write data, and the modifying of existing buffer data, are described in
"Orders and Attributes" on page 4·10.
Erase/Write Command
An Erase/Write command causes both an erase and a write operation. The erase
operation clears the device buffer to nulls, positions the cursor to location 0, sets the
buffer address to 0, and sets the screen size to the default size, if the default size is
not currently in effect. The write operation is then performed in the same manner as
for a Write command. If the data does not contain a WCC byte, the Erase/Write
command does not cause the buffer to be erased.
Erase/Write Alternate Command
If the 3708 is configured for large screen emulation (3270 model emulation
=
3, 4,
or 5), the Erase/Write Alternate command does the following:
• Clears the device to nulls
• Positions the cursor to location 0
• Sets the buffer address to 0
• Puts the display in the alternate emulation mode type defined by the BIND (if
the alternate size in not already in effect).
If
the 3708 is not configured for large screen emulation (3270 model emulation
=
2),
the Erase/Write Alternate command is treated as if it were an Erase/Write command.
Erase All Unprotected (EAU) Command
This command does the following:
• Clears all the unprotected character locations to nulls and sets any character
attributes affected to their default values.
• Resets to 0 the MDT bit in the field attribute for each unprotected field.
• Unlocks the keyboard.
• Resets the Attention Identification (AID).
• Repositions the cursor to the first character location, after the field attribute, in
the first unprotected field of the device buffer.
If the entire buffer is protected, buffer data is not cleared and MDT bits are not
reset. However, the keyboard is unlocked, the AID key reset, and the cursor is
repositioned to the first buffer address.
Note: The EAU command does not have a WCC after it.
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IBM 3708 Description
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