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position. The second use is the count register for the decrement and skip-on-zero (dsz) instruction. The interpreta-
tion for these two uses is shown below:
load count register (Idc)
load threshold
threshold off
Idc
The
and
threshold instruction 1536 must be executed after all uses of
the next graph command is executed. If the load threshold is not executed, the thresh-
old may not function correctly.
DATA WORDS
Data words are differentiated from instruction words by the two most significant bits, bits 11 and 10. The following
words are data words:
Interpretation of these data word formats by the CRT refresh program depends entirely on the preceding instruc-
tion word.
Graph.
Each data word following a graph instruction is interpreted as an absolute y position. Y position values
follow the general rule shown below:
positive data, displayed
positive data, blanked
negative data, blanked
NOTE
instructions use the THRESHOLD level register. Therefore, load
8
7
11
10
9
0
0
x
x
x
x
x
x
9
8
7
6
5
4
Idc
dsz,
and
8
7
6
5
4
3
6
5
4
3
2
1
0
x
x
x
x
x
x
x
x
x
x
3
2
10
and before
2
1
0
2048 + yposition
4096 - y magnitude
(a two's complement value)
A p p e n d i x 1 1
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