Mallinckrodt NELLCOR NPB-4000 Service Manual page 136

Section 13: Microprocessor Computer and Control –Theory of Operation
13.15.4 CS5# + A RESET KNOB INT/READ PUSH SWITCHS
13.15.5 CS5# + C Write Enables WDT/READ Push Buttons
13.15.6 CS5# + E WRITE NSCALL/PTRRST/READ PUSH SWITCHS
13-22
Bit 7 resets the A/D converter and is generated when software starts a conversion
sequence.
The I/O address of CS5# + 6 has two functions associated with it. Writing to
this register generates a KNOB_INT_RST signal which resets the knob interrupt
flip flops. This would be done by software after a knob interrupt occurs.
The software polls this register every 50 millisecond and looks to see if the
PB INT bit (bit 6) or the KNOB INT bit (bit 7) is set true, indicating that a
switch has been pressed or that the knob is being rotated. If either of these bits is
set true, then the software just looks at bits 3, 4, and 5 to determine which of the
knob functions has occurred. If the PB INTB is set true, then register C must be
read to determine which switch has been pushed.
Register CS5# + A has the following bit assignments:
Bit 0 Not used
Bit 1 Not used
Bit 2 Not used
Bit 3 Knob push button switch
Bit 4 Knob channel B rotation
Bit 5 Knob channel A rotation
Bit 6 Push Button occurred
Bit 7 Knob rotation occurred
After powering up, the software must enable the watch dog timer function by
writing to this register. The act of writing to CS5# + C automatically sets the
WDT flip flop to a 1 and enables the WDT time out function.
Reading this register gives the push-button status, as well as the state of the
WDT flip flop.
Register CS5# + C has the following bit assignments:
Bit 0 Not used
Bit 1 Not used
Bit 2 Not used
Bit 3 WDTEN (Watch Dog Timer Enable)
Bit 4 LCD Contrast switch
Bit 5 Audio Volume switch
Writing to this register sets or resets the nurse call and printer reset bits. To set
NSCALL, write a 1 to bit 7, and to reset NSCALL write a 0 to bit 7. To reset the
printer, write a 1 to bit 6. To reset this bit write, a 0 to bit 6.
The bit assignments for reading this register are shown below. The bit
assignments for writing the NSCALL and PTRRST are different from the read
assignments.