Hill-Rom VersaCare P3200, Service Manual

Page: 124 / 379

Electrical System
Chapter 3: Theory of Operation
SPI_IN is the data line for writing to the pendant, which is on pin 7 of the P1
connector. Commands that will be written to the pendant are nurse call and
nurse answer.
SPI_OUT located on pin 8 of the P1 connector is the serial data being read
from the pendant. This line provides the patient commands to the bed, such as
head up, head down, knee up, knee down, room or read lighting, TV, and radio.
The output also has a tri-state buffer attached to the line, which allows the data
to be routed to the logic board or to be held if the pendant is not selected by the
pendant CS line.
SideCom® Communication System
Power is supplied to the SideCom® Communication System by the P3200
central power supply. The power supply provides a pre-regulated 8.2 ± 0.2
VDC referenced to signal GND at 400mA max, 200mA typical. The GND is
common among all nodes in the bed.
All of the Scale and PPM functions revolve around the microprocessor on the
control board. This is an 8051 variant with internal 32K flash program and 256
+ 1.2K EEPROM data memory. External to the microprocessor are the CAN
transceiver, UTV chip, watch dog reset circuit, SideCom® Communication
System relays, and audio attenuator with 16 volume settings.
Scale and Patient Position Monitor
Power is supplied to the Scale/Patient Position Monitor (PPM) system by the
P3200 central power supply. The power supply provides a pre-regulated 8-9 V
DC referenced to signal GND at 400mA max, 200mA typical. The GND is
common among all nodes in the bed. This is important to the network
transceiver explained later.
The analog circuitry is a single chip solution specially designed for scale
transducers. It is located in the frame of the bed as close to the load beams as
possible. The load beams are resistive bridge sensors excited by a regulated
DC voltage. This regulated voltage is supplied to the beams and to the A/D
converter reference input to minimize the effects of variations.
Each beam is connected to the differential input on the A/D. The Mux and
Gain (up to 128) is internally configurable through software. The A/D has the
ability to detect open or shorted sensors. The part has a second stage sigma-
delta converter. The serial interface is SPI compatible which transfers the data
to the embedded controller.
Page 3 - 10 VersaCare™ Bed Service Manual (MAN333 REV 2)