Texas Instruments 990 Manual page 108

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945424-9701
All cursor commands except A and I affect only the cursor position and provide no additional
information. Cursor commands, A and I, cause the current cursor address to be read and
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the new cursor location. Cursor command, A, permits a new entry after each cursor move
operation. The cursor command, I, continuously writes the operator-selected cursor address into
the controller register.
Modify VDT Memory/Scope Loop Verb (CD). The Modify VDT Memory/Scope Loop Verb (CD
verb) assists the operator in the isolation of a system or unit fault. The CD verb allows the
operator to modify the data at the current cursor address which may point to any address
(displayed or not displayed) in VDT memory. The CD verb can also activate useful routines for
scoping. The CD verb has five commands, as follows:
•
S - Read or read and modify memory character at current cursor address.
• R - Read or read and modify memory character at current cursor address and move
cursor right one position.
• F - Free form input mode.
• SL - Modify and read data at cursor address.
• C -
Exercise CRU interface.
• D -
Write pattern to screen (Japanese Katakana model only).
The command S aliows the operator to read memory data at the current cursor address and to
write new data at that location without changing the cursor address. The data in the read data
register following this operation is the result of a CRU data transfer, not an actual memory read
operation. Figure 2-3 illustrates the entry of the five CD verb commands.
The command R. reads the memory contents at the current cursor address and allows the
operator to modify the memory contents at that location. The command then increments the
cursor address and reads again.
The command. F permits free-form input to the screen from the terminal's keyboard. The
command is initiated from the hot mock-up system's 733.
The command SL reads refresh memory at the current cursor address and allows the operator
to modify memory at that location (memory write). Following acceptance or modification of the
data byte, the program continuously cycles performing a write followed by an increment and
decrement of the cursor address to cause memory read operations. This loop permits scoping of
a memory
pattern.
The command C exercises the CRU address bits (and word select circuitry) in a tight loop for
scoping.
2-6
Digitai Systems Division