Marquette CardioServ Serviceanleitung Seite 50

Marquette Hellige GmbH CardioServ V. 3 Page 9
- generation of power supply voltages for the recorder
- processing of all signals for the printer microcontroller
Further circuit components on the PCB are :
- generator of 5 V from 12 V via an integrated switching controller, short-circuit-
proof and protected against overvoltage by Transzorb diodes
- sound generator, frequency controlled by SW
- RS-232 interface, protected against overvoltage by Transzorb diodes. Interface
integrated into microcontroller, external conversion of level from 5 V to +- 12 V.
- energy selector switch, binary coded, delivers its information to PCB Analog and
to the microcontroller
- keyboard interface to connect the membrane keypad
- control of LEDs on the keypad
- watchdog
- reset generation, when +5-V supply drops below 4,65 V or exceeds 5,5 V
- RAM buffering by battery when instrument is switched off
- options interface for pacemaker and SpO2.
PCB Pacemaker (38802874)
The CONTROLLER block acts as a microcontroller system. STIMCON is equipped
with the parallel-to-serial converter, the analog protective circuits and some glue
logic. Control of the optoelectronic coupler, protective circuit against DC stimulation
with integrated powerdown of the floating part, DC/AC conversion and the floating
part are hidden behind the FLOATING part. The function of each connection is
shown in a table.
The chips required for the microcomputer system are listed on the CONTROLLER
sheet. Excluded is the address decoder which, for clarity's sake, is included in the
STIMCON plan.
The main component is the microcontroller 8032 (Z501). Contrary to the 8052, it
requires an external program memory store, here integrated into the circuit in the
form of a 32-kbyte EPROM (Z502). An external, static RAM (Z8) is envisaged, also
with a capacity of 32 kbytes. This provides sufficient memory space to save
graphics displays, such as the plethysmogram, generated by the SpO2 module.
Integrated into the system is a watchdog, MAX695 (Z1). This must be reset at least
every 1.6 s since, otherwise, a processor reset of 50 ms duration is released by
pins 15 and 16 (RESET, RESET_). A reset is also released when the supply
voltage at pin 9 (PFI) drops below 4.75 V, since under this level the integrated
circuits no longer operate within their specific dynamic ranges, thus failing to ensure
reliable function.