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TELEDYNE API
Theory of Operation M703E Calibrator Operator’s Manual
DISPLAY DATA DECODER
This decoder translates the serial data sent by the CPU (in TTY format) into a bitmapped image that is sent over
a parallel data bus to the display.
DISPLAY CONTROLLER
This circuit manages the interactions between the display data decoder and the display itself. It generates a
clock pulse that keeps the two devices synchronized. It can also, in response to commands from the CPU turn
off and/or reset the display.
DISPLAY POWER WATCHDOG
The M703E calibrator’s display can begin to show garbled information or lock-up if the DC voltage supplied to it
falls too low, even momentarily. To alleviate this, a brownout watchdog circuit monitors the level of the power
supply and in the event that the voltage level falls below a certain level resets the display by turning it off, then
back on.
9.4. SOFTWARE OPERATION
The M703E calibrator’s core module is a high performance, 386-based microcomputer running a version of
DOS. On top of the DOS shell, special software developed by Teledyne Instruments interprets user commands
from various interfaces, performs procedures and tasks, stores data in the CPU’s memory devices and
calculates the concentrations in the sample gas. Figure 9-11 shows a block diagram of this software
functionality.
DOS Shell
API FIRMWARE
Calibrator Operations
Calibration Procedures
Configuration Procedures
Autonomic Systems
Diagnostic Routines
Memory Handling
Calibration Data
System Status Data
Interface Handling
Sensor input Data
Display Messages
Keypad
Analog Output Data
RS232 & RS485
External Digital I/O
Measurement
Algorithms for
photometer
CALIBRATOR
HARDWARE
PC/104 BUS
PC/104 BUS
Figure 9-12: Schematic of Basic Software Operation
150 05744 Rev B