Definition Of Terms; Figure 9-6: Display Control Block Diagram; Figure 9-7: Printer Control Block Diagram - Mallinckrodt Nellcor N-20 Service Manual

9.6.3 Display Control Block Diagram (Figure 9-6)
The N-20/N-20P display is controlled by the display control circuitry (see Figure 9-6). A sensor is
used to measure ambient light. During low light conditions, the display backlight, an
electroluminescent device, is automatically switched on.
Main PCB
Microprocessor
9.6.4 Printer Control Block Diagram (Figure 9-7)
Printer circuitry (Figure 9-7) is divided into two subsections: the printer interface and the printer flex
circuit. The printer interface circuitry is present on all models, but is disabled by software in the N-20.
The printer flex circuit is added when a printer is present.
Main PCB
Microprocessor
9.7

Definition of Terms

9.7.1 Analog to Digital (A/D) converter
The CPU has a 10-bit A/D converter on board. Up to eight different analog inputs can be provided to
the A/D for measurement.
9.7.2 Central Processing Unit (CPU)
An Intel 80C196KC 16-bit microcontroller. The CPU sends and receives control signals to the SpO
analog section, display, and optional printer.
Main PCB
Control
conditioning
circuit
(generates
timing
signals)
AUX PCB
High voltage
control circuit
(enables
+70 VDC
to display)

Figure 9-6: Display Control Block Diagram

AUX PCB
Printer
interface

Figure 9-7: Printer Control Block Diagram

AUX PCB
Display driver
(1)
Display driver
(2)
70 volts
N-20 only
Printer
flex
circuit
(N-20 only)
(N-20P only)
PCB
On ADV D/D
User push buttons
Technical Supplement
Display
Display
backlight
Printer
2
9-5