6530 Programmer's Guide

Block Mode Operation
3-4
6530 Programmer’s Guide
Your application can also set the MDT for either an unprotected field or
a protected field with the data attribute character for that field. This
allows your application to always read a certain unprotected field or to
read a certain protected field along with modified unprotected fields to
ensure screen integrity. For example, you can define fixed data, such as a
form identifier, as a protected field with the MDT bit set in the data
attribute for that field. (To inhibit display on the screen, the field can be
defined with an invisible video attribute.) When your application reads
the page, the 6530 transmits the form identifier field as well as any
unprotected fields that have been modified by the user.
Data Types The data type attribute defines what type of data may be entered from the
keyboard into an unprotected field. For example, the data type attribute
can be set to allow only numeric data to be entered into a particular field.
No data type checking is done for data sent from your application.
As data is entered from the keyboard, the 6530 checks each character to
determine whether it falls in the range of valid characters for the selected
data type. If the character is valid, the 6530 writes the character into the
field and continues processing. If the character is invalid, the character is
not written into the field; instead, the 6530 sounds the audible alarm and
displays an error message (INVALID DATA) in the error line. (The
message is cleared on the next keystroke.)
The data type is set by three bits in the data attribute character. Eight
different data types are available (0-7). The 6530 uses a predefined data
type table, which specifies the displayable characters that are valid for
each of the data types. If necessary, your application program can also
redefine the data type table using the Esc r sequence.
Table 3-1 lists the predefined data types and summarizes the characters
that are valid for each type. (Appendix D contains the complete table.)
“X” indicates the characters that are valid for the data types listed in the
first column.
Note A program or system reset, mode or submode switch, or
reinitialization (Esc q) restores the predefined data type table.