Spacelabs 91518, Руководство по обслуживанию

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91518 Multigas Analyzer Service Manual 3-3
Theory
Interface PCBA
The interface PCBA (P/N 670-1319-xx) provides power to and controls the gas analyzer unit. The interface
PCBA is responsible for the two-way SDLC communication link with the Spacelabs Healthcare monitor. The
interface PCBA transmits processed data from the gas module to the monitor for display and recording.
Main CPU (MCU)
A Motorola MPC850 is the main CPU on the board.
EEPROM Circuit
The EEPROM stores configuration and setup information.
Serial Number IC Circuit
A serial number is available to be read by the MCU and then passed onto the host monitor upon demand. The
one-wire interface provides power through the pull-up resistor to the S/N IC. Data is bi-directional over this line.
This has no significance when replacing the PCBAs.
PCB Version Detection
The PCB codes the board version by selectively connecting each of the six lines either Hi or Lo, to form an ID
code. This is read and used by the software and passed to the host monitor upon demand.
Reset Circuit
A power-ON reset circuit provides a reset while the ISO_3.3V_CPU is coming up. The reset continues for an
additional 180 msec after the supply has reached the 3.0 V level or higher. If the supply drops below this level,
the circuit will again reset and reinitialize the 180 msec timer. Power Fail is implemented by monitoring the
+5 V supply and issuing a non-maskable interrupt (NMI) to the processor when the power supply goes low.
Data Lines - Power-Up Reset Configuration
During /HRESET, the MCU configuration is set by reading the data lines. /HRESET occurs at analyzer power
ON or reset.
Power Fault Detection
A low voltage fault on incoming ±12 V power supplies is determined by a pair of comparator circuits that
compare a divided-down sample of each supply to the reference voltage. When a fault occurs, an interrupt is
sent to the MCU.