Tektronix DAS 9221 Option 04, User Manual

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Reference
DAS System User Manual
3–39
Pattern symbols describe a pattern of bits. Each bit in a pattern symbol can be 0,
1, or X (don’t care). Pattern symbols are used when a group of signals define a
logical state. For example, a microprocessor has a set of pins that indicate the
type of bus cycle in progress. A memory read cycle may be indicated when the
RD~ and MREQ~ pins are 0 (logic low) and the BUSAK~ and M1~ pins are 1
(logic high). You can define a pattern symbol name called mem-read that
corresponds to bit pattern 1100 and thereby mark all memory read bus cycles in
the State display menu. For other bus cycles the logic state of these pins is also
important and you can define different bit patterns for each cycle type.
To use symbolic names in module setup and display menus, you must first
perform the following tasks:
1. Create a symbol table using the Symbol Editor menu, or transfer a symbol
table to the system from a host computer.
2. Specify the Symbolic radix for the appropriate channel group in the Channel
menu. A new File field will appear allowing you to name the symbol table to
be used for this channel group. Only one symbol table per channel group is
allowed, but each channel group can have its own symbol table.
3. You can now use symbolic names to define word recognizer events in the
Trigger menu. After making an acquisition, you can view symbolic values in
the State or Disassembly display menus.
When you first enter the Symbol Editor menu, the default pattern-type symbol
table is displayed. You can immediately begin editing this menu. Alternatively,
you can select function key F2: FILE FUNCTIONS to create a new symbol table
or to open an existing symbol table to edit. Be aware, however, that many
applications (microprocessor disassembly programs) supplied with symbol tables
are write protected and can only be opened as read-only files.
The Symbol Editor menu provides a variety of function keys that you can use to
help create, edit, and search for symbol and pattern values. Selecting function key
F3 changes the definition of the function keys from edit mode to search mode.
Figure 3–18 shows a pattern-type symbol table.