Mallinckrodt NELLCOR NPB-4000 Service Manual page 159

14.13.4 CS5# + A RESET KNOB INT/READ PUSH BUTTONS
14.13.5 CS5# + C WRITE ENABLES WDT/READ PUSH BUTTONS
Bits 0-3 were defined in the above paragraphs. Bit 4, BCK_LITE_ON is a bit
that turns on the LCD backlight when set to a 1. When powered on this bit is 0
and the backlight is off. To turn on the backlight this bit must be set to a 1.
Bit 5 enables the clock going to the front end transformer, which generates the
isolated front end voltages. If the front end should ever go into a base line
condition, it is reset by stopping the clock to the transformer and the front end
voltages will go to 0. Turning this bit back on powers the front end up and
essentially acts as a reset.
Bit 6 enables programming of the boot flash. This would be used if a new
executable program were downloaded via the RS-232 channel and stored in the
executable flash.
Bit 7 set causes the A/D converter chip select to be set and clears STYXCLK
signal. Bit 7 cleared causes the A/D converter chip select to be cleared and starts
a conversion sequence.
The I/O address of CS5# + 6 has 2 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 ms and looks to see if the PB_INT bit
(bit 6) or the KNOB_INT bit (bit 7) is set true, indicating that a button has been
pressed or the knob is being rotated. If either of these bits is true the software
must look at bits 3, 4, and 5 to determine which of the knob functions occurred.
If the PB_INT is set true, then register C must be read to determine which button
was 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
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 one 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.
Section 14: Main Color Board Digital Theory of Operation
14-19