Mallinckrodt NELLCOR NPB-4000, Service Manual

Page: 137 / 219

Section 13: Microprocessor Computer and Control –Theory of Operation
13-23
Register CS5# + E has the following bit assignments
Bit 0 Not used
BIT 1 Not used
BIT 2 Not used
BIT 3 Not used
BIT 4 Not used
BIT 5 NURSE CALL
BIT 6 PRINTER RESET
BIT 7 PRINTER CTS (CLEAR TO SEND)
The NURSECALL and PRINTER RESET bits are the flip flop outputs
programmed by writing to register CS5# + E as explained above.
A 1 (high) indicates that the bit is true, a 0 that the bit is false.
13.16 DIGITAL SCHEMATIC FIGURE 17-5 THROUGH FIGURE 17-7
These schematics include all of the above circuits and some additional circuits
that need explanation. For clarity purposes we will discuss the page 1 and
integrate page 2 wherever necessary.
Page 1 of the schematics is mostly the digital portion of the design. It contains
the following chips:
386EXMP microcontroller
ACT1000F programmable device with the control circuits
LCD
CONTROLLER 1351FLB LCD display control chip
74HCT244 buffer chips for the signals from the LCD
controller to the display itself
74LVC16245 data bus buffer to interface the 386EX to the other
chips
RTC DS1693 real-time clock with 64 bytes of battery-backed
ram and on-board crystal
74LVC541 mux for the address/data to the RTC
DUART dual UART for the RS-232 and recorder
MAX211E RS-232 interface chip with 15,000 volts ESD
DISPLAY RAM 32K x 8 SRAM for the LCD display
DRAM 256K x 16 dynamic ram memory
74ACT157 address mux for the DRAM
BOOT FLASH bootable/executable flash memory
TREND FLASH flash memory for storing trend data
OSCILLATOR 40 MHz oscillator to generate CLK2