Roll Up Screen - Texas Instruments 990 Installation And Operation Manual

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945423-9701
3.6.9 ROLL UP SCREEN. The following code sequence moves the data displayed on the screen
upward one line, shifting the top line into nondisplayable memory, and fills the bottom line with
specified data.
RO
Rl
R2
CURSOR
DTASTB
WRDSEL
MAXLYN
BUFF
LSTCHR
LNCNT
WRTCHR
EQU
EQU
EQU
EQU
EQU
EQU
EQU
BSS
DATA
SBO
LDCR
SBZ
LI
LI
LI
LDCR
STCR
SBO
SBO
DEC
DEC
JNE
DEC
JNE
0
1
2
>A
>8
>F
24
80
1920·1
WRDSEL
@LSTCHR, 11
WRDSEL
RO,MAXLYN
Rl,80
R2, BUFF
+
79
*R2,8
*R2,8
DTASTB
CURSOR
R2
Rl
WRTCHR
RO
LNCNT
3-19/3-20
Workspace register 0
Workspace register 1
Workspace register 2
Move cursor.
Data strobe
Select word (0=0; 1=1).
Screen size = 24 lines.
Buffer filled with new bottom line
Last character position for 1920·
character display.
Select word 1.
Set cursor address to last character
position.
Select word 0.
24 lines will be rolled.
80 characters will be replaced.
Address of last character in buffer
Write last buffer character to screen.
Read last visible screen character.
Strobe last buffer character to screen.
Move cursor left one position.
Decrement buffer address.
Decrement column count.
Repeat 80 times.
Decrement line count.
Move each line up one position.
Digital Systems Division