Tandy 1400LT - Page 285

SPRITE ORIGIN (H O.V=O)
-----_________
t
L-
I
I
SCREEN
'4 I'\i ACTIVE
I AREA
, 16dots
2. Sprite Pattern Data
Two 16
X 16 dot patterns for the SPRITE can be defined in the Register Bank. One is the ANDing pattern, anded
with the displayed screen pattern. The foreground color of this pattern is selected by the S1 SPRITE color of the
SPRITE COLOR SELECT register (hex 68) in this Register Bank, and the background color of this pattern become
white (all
1).
The second pattern is the EXORing pattern, which is exclusive-ored with the anded result of ANDing pattern and
the screen pattern. The foreground color of this pattern
is selected by the S2 SPRITE COLOR of SPRITE COLOR
SELECT register and the background color of this pattern becomes transparent.
The following indicates the relation
of the pattern and register data address.
Pattern Origin
Pattern Origin
D7 DO D7 DO D7 DO D7 DO
1E
1F
20 21
22 23
3E 3F
(HEX) (HEX)
AND Pattern EXOR Pattern
3. Test/Sprite Control Register
This is an
8 bit write only-register. Its address is hex "64" within the Register Bank.
The following
is a description of the Test/SPRITE CONTROL REGISTER function.
BIT NAME FUNCTION
0 BL SPRITE BLINK ENABLED
1 S1
ON SPRITE 1 (AND PATTERN) ENABLED
2 S2 ON SPRITE 2 (EXOR PATTERN) ENABLED
3 ss 0 SMOOTH SCROLL OFFSET 0
4 ss 1 SMOOTH SCROLL OFFSET 1
5 ss 2 SMOOTH SCROLL OFFSET 2
6 TEST
0 SELECT TEST MODE
7 TEST 1 (MUST BE ZERO)
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