Accutorr Plus Service Manual - Mindray

2.2.7 Communication Board
The Accutorr Plus Communication module provides the communication signal interface
between the LED/CPU board, 0670-00-0650-01, and the external communication
interface connectors. The board supports the CIS/HI/DIAP interface via RS-232E, provides
a feed through path for the Datascope proprietary download connector, DC/DC converter
for the +12 Vdc @ 100 mA required for wireless telemetry controlled by the CPU and
includes the driver for an external isolation relay that is activated by Nurse Call (future
option).
The RS-232E interface, used for DIAP, is implemented using a Maxim, MAX239
Multi-Channel Transceiver (U2). This chip has a minimum 10 volt output signal level,
which provides a safe operating margin above the 5 volt minimum RS-232 operating signal
level. Communications is to support a 5 wire interface, 4 signals and a ground. The
signals are described below:
All RS-232 signal are ESD protected by a U3, an SM14M24C Transient Voltage
Suppressor array. The +12 Vdc power required by the MAX239 is supplied from the
on board DC/DC converter. In addition the MAX239 requires 5 Vdc for the internal
logic. This is supplied as an input to the communications module. The MAX239
receivers are controlled by logic signal CSTAT*. Logic 0 enables the receivers, otherwise
they are tri-stated.
The RS-232 signals appear on connector J2, a dual row 5 pin header which will have
a mating 10 pin pendant ribbon cable attached. The other end of the ribbon cable
assembly is a 9 pin panel mount `D’ connector. Included on this connector are pins for
the future Nurse Call option. See chart for pinout.
The Accutorr Plus software is upgradable via a three wire download communications
interface. The required drivers are located on the LED/CPU board and only a signal path
is provided to the external interface connector. ESD protection for the signal lines is
provided by part of U3. Communications is to support a 3 wire interface, 2 signals and
a ground. The signals are Tip being transmit, Ring is receive and shield is ground.
The on board DC/DC convertor provides +12VDC power required for wireless telemetry
that will be a future feature available for Accutorr Plus as well as some local circuitry.
The DC/DC converter is implemented using a Maxim MAX1771 DC/DC controller used
in the Buck/Boost configuration. The supply is designed to deliver 12 Vdc @ 100 mA
minimum. When the SHDN pin (U1-4) is high the MAX1771 enters the shutdown
mode and its output is approximately zero volts. The shutdown mode is controlled by
the state of either of two logic signals NCALL* or CSTAT*. If either of the signals is
logic 0, the DC/DC converter will operate normally.
2-26 Revised 12/20/00
Accutorr Plus Service Manual
Chapter 2 - Theory of Operation