Datascope System 98 Service Manual page 144

e Configuration Switch
There is an eight position DIP switch on the Main Board that 1s used to set
certain default conditions for the software, such as language and modem
selection. The settings of this switch are readable by the 68020 CPU. This function
occupies | byte address on the 68020's bus. This switch is accessible by removing
the Display Controller shield.
6809 (IAB) Subsystem
The 6809 (IAB) subsystem provides for the control of the inflation and deflation
of the balloon via control signals passed to the Solenoid Driver PCBA as well as
the generation of the audible Alarm/Alert tones.
9 Major Functions
- The 6809, a 8 bit microprocessor
- Clock Generation Circuit
- Reset/Warchdog Timer
- Program memory on removable Datasette (SOK X 8) accessible any time
- Read/write data storage of 12K bytes
- Bus Control PLDs
- Versatile Interface Adaptor (VIA)
- Alert Tone Generator & Alarm
- Pump Motor Controls
- Control Register
- Status Buffers
~ Shared RAM
e Central Processing Unit
The CPU is a Motorola MC68B09 8 bit processor with an external clock rate of
8MHz (running internally at 2mHz). It has a 16 bit address bus which allows it
to directly address up to 64K bytes of physical memory and/or peripheral devices.
The 6809 processor always fetches instructions and executes them directly out of
the 8 bit Datasette, see below.
e Clock Generation Circuitry
The 8MHz processor clock is derived from the 16MHz 68020 CPU clock. The
CPU generates the two-phase E and Q clocks which are utilized by the Bus
Control function.
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System 98 Service Manual
Chapter 2, Theory of Operation