HP HP-97 - Printer

Theory
of
Operation
HP-97
signals from the ACT. 224 program steps of 8 bits each are stored in ROMS
1, 2, 3, and 5, which contain program memory.
2-19. Data is stored in the 24 storage registers of 56 bits each located
in ROMs 1, 2, 3, and 5. ROM 1 is the primary register; ROM 6 is the secondary
register.
2-20. PRINTER
2-21. The printer used in the HP-97 employs a very hot source (print head
resistors) in close contact with heat sensitive paper. This paper changes
color in the area of heat contact.
2-22. The print head contains seven small resistors (each about 10 ohms)
that heat up when current is passed through them. Figure 2-6 shows the
print head and resistors.
2-23. The head is mechanically moved across the paper by a lead-screw
mechanism (see figure 6-2). By passing current through the appropriate
head resistor at the correct time, as the head moves across the paper,
characters are thermally printed (see figure 2-7).
2-24., Notice the slight slant of each character. This is done to decrease
instaneous current demands. The printer/interface and keyboard buffer
(PIK) is responsible for this operation. The PIK also controls print
intensity, line width, and motor movement commands.
Resistors
(Common)—
Figure 2-6. Print Head
2-6