Keyboard Codes - Texas Instruments 990 Installation And Operation Manual

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945423-9701
Table 3-2. Built-In Test Input Signals
Input Signal
Video
Horizontal
Sync
Vertical Sync
Audio Alarm
Test Mode
Word 0
CRU Bit*
Oorto
o
o
*CRU bits 0 and 1, word 0, selects the test signal for VDT O.
CRU bits 10 and 11, word 0, selects the test signal for VDT 1.
3.4 KEYBOARD CODES
CRU Bit*
lor 11
o
o
Signal
Characteristics
NOTE: Program Initializes
Memory
O=AlI memory locations con-
tain SPACE character (HEX 20)
I=AlI memory locations con-
tain EM character (HEX 19)
0=52·microsecond duration
pulse
1=12·microsecond duration
pulse
0=16.4-millisecond duration
pulse at 60 Hz or 19.8·milli-
second pulse at 50 Hz
1 =192-microsecond duration
pulse
o
="BEEP" off
1 ="BEEP" on; each pulse 0.3
second duration
Striking an alphanumeric or function key on the keyboard causes a character to be transmitted to
the' VDT controller. The character is transmitted serially as an 8-bit byte. Seven bits are used for
data and an eighth bit for control. When the control bit is OFF (logic
0)
the seven data bits repre-
sent the I 28-character ASCII set. When the control bit is ON (logic I), the data represents special
.characters such as cursor up or function key Fl. On the Japanese keyboard, the control bit selects
the Katakana character set shown in figure F-9, Appendix F.
The REPEAT key on the keyboard does not produce a character. Depressing this special key in
conjunction with any other key causes the character associated with that key to be generated at
a rate of
10
±
2 characters per second.
Table 3-5 shows the codes produced by the United States keyboard. Figures 3-6 through 3-9 depict
key position interpretations for various modes of operation. The modes of operation are controlled
by the SHIFT, CONTROL, and UPPER CASE LOCK keys. The character positions and associated
codes used with the international keyboards are illustrated in the appendixes. The Japanese key-
board has mode-select switches for the alphanumeric or Katakana mode, and an indicator lamp in
the switch lights shows when the Katakana mode is selected.
3-6
Digital Systems Division