Texas Instruments 990 Installation And Operation Manual page 42

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945423-9701
Bit Number
Table 3-3. Model 911 VDT Controller Addressable Output Bits (Continued)
Description
Cursor Move - permits the cursor address register to be incremented or decremented
with a single-bit transfer instruction. A logic 0 output causes the cursor address to in-
crement. A logic 1 output decrements the cursor address.
NOTE
Do not send write data strobe and cursor move within a single LDCR operation.
The issue of separate commands assures completion of the write operation be-
fore the cursor address changes.
The cursor address register range is between 0
16
and 3BF
16
for a 960-character
display and 0
16
and 77F
16
for a 1920-character display.
Note that locations 3C0
16
to 3FF
16
on the 960-character display and 780
16
to 7FF
16
on the 1920-character display are not displayable. These locations
may be accessed by software. Software must detect when an increment or
decrement of the cursor address register will move the cursor into the non-
displayed region.
Blinking Cursor Enable - controls the blinking of the cursor. If the cursor is dis-
played, a logic 1 on this bit causes the cursor to blink at a 2-hertz rate. A logic 0 dis-
ables the blinking cursor. Blinking results from alternately displaying the cursor posi-
tion character in normal and reverse video.
Keyboard Interrupt Enable - controls whether a keyboard data ready signal generates
a CRU interrupt. Logic 1 enables an interrupt, while logic 0 masks the data ready in-
terrupt. Only the selected VDT keyboard logic is affected.
Dual Intensity Enable - controls dual intensity on the VDT screen. Logic 0 selects
high intensity for the entire screen. Logic 1 selects high intensity for all words in
refresh memory with bit 7 not set, and low intensity for all words with bit 7 set.
On the Japanese model, dual intensity is disabled by this bit being set to a logic O.
Display Enable - logic 1 enables data to be displayed on the VDT screen. A logic 0
blanks the screen. A master reset automatically sets display enable to logic
O.
Select Word - The function of any CRU interface line is determined by the type of
operation (input or output) and the select word signal level. Figures 3-1 and 3-2 and
34 and 3-5 show the two functions assigned to each input and output bit. The 32
input and 32 output lines on the CRU interface associated with each VDT are grouped
into 16-bit words. The first set of inputs or outputs is selected when select word
=
0,
and the second set of interface signals is selected when select word
=
1.
NOTE
The following descriptions of the CRU bit functions assume that word select has
been set to logic 1.
3-10
Digital Systems Division