HP 262SA - Graphics Data Format

A.) Tektronix 4010
(0,779)
.---------~ (1023,779)
:...-74 Characters-':
3s
(0,0) L..::::....- ---I (1023,0)
798,720 Points
2590 Characters
Graphics
S.) HP Terminal
(0,389)
r-:----------, (511,389)
:...- 80 Characters--":
24
(0,0) L..::.: -" (511,0)
199,680 Points
2847 Characters
Figure D-20. Comparison of The 4010 And The HP Terminal
Graphics Data Format
In Compatibility mode the graphics data is formatted as two-byte coordinate values. The lower
five
bits of each byte are used to make a 10 bit (0-1023) coordinate. Data sent to the terminal
must have the "Y" coordinate sent first; <Upper Y> <Lower Y> <Upper X> <Lower X>.
When data is returned to the computer (cursor position, etc,), the X coordinate is returned first;
<Upper X> <Lower X> <Upper Y> <Lower Y>.
Data bytes sent to the terminal use bits 6 and 7 to indicate the byte is an Upper byte, a lower Y,
or a lower X. Bit 8 (parity) is not used.
Bits
7
6
0 1
Upper
X
or Y
byte
1 0 Lower X
byte
1 1
Lower Y
byte
These identifying bits allow you to send only the changed portion ofa four byte address. The
following data bytes must always be sent:
• Lower X byte
• Any changed byte
• Lower Y byte if the Upper X byte has changed
Table D-14 can be used to determine address bytes. For example, to plot the points A (0,0), B
(0,31), C (256,31), D (256,0)
the sequence shown in figure D-23 is used:
D-49