Chapter 2 Circuit System
11
Fluorophos® ALP Test System Model FLM300 Service Manual
code determines if new software will be downloaded by
checking if the dip switch is in the “PROGRAM” position.
If it is, the boot code waits for new software to be
downloaded through the serial port. If not, the
application code starts. The real time clock maintains the
current date and time, and contains nonvolatile memory
where the instrument’s operation parameters are stored.
A internal lithium battery preserves the contents of the
nonvolatile memory when the instrument is turned o.
Finally, the read-write memory is used for stacks,
variables, etc., except for the small section allocated for
the interrupt vectors. The interrupt vectors tell the
processor what code to run when an interrupt occurs,
and functions similarly to the reset vector.
Please note that all memory addresses and sizes are
always defined in terms of bytes, even though the
processor handles words (1 word = 2 bytes, 1 byte = 8
bits; therefore, 16 bits = 1 word).
Input/Output Map: The 64 kilo-bytes of I/O address
space control access to all peripherals such as the serial
ports, application board, etc. The processor uses 256
bytes, called the Peripheral Control Block, to control the
integrated serial ports, timers, interrupts, chip selects,
and I/O pins. The Peripheral Control Block is fully
described in the 80C186EB/80C188EB Microprocessor
User’s Manual. The application board’s registers and the
CPU board’s registers control access to various functions
and are described later.
Memory: Two types of memory are available: read-only
and read/write. The chips used here have 8-bit wide data
buses. Used in pairs, the memory becomes compatible
with the processor’s 16-bit wide data bus. The read-only
memory is implemented using two 128 kilo-bytes x 8 bits
Flash EPROMs. Flash memory is only programmable
when a programming voltage (in this case, 12 volts DC) is
applied to the memory; otherwise, it behaves like
read-only memory. The boot code controls the
programming voltage, since this is the only place where
new software can be downloaded. The read/write
memory is implemented using two 128 kilo-bytes x 8 bits
static RAMs.
Watchdog Timer: The watchdog timer provides a
mechanism to reset the processor when the software is
not behaving normally. The software “pets” the
watchdog every 100 - 200 milliseconds. As long as the
watchdog is “petted”, nothing happens. However, if the
software stops “petting” the watchdog, the watchdog
“bites” the processor by activating the processor’s
RESET pin, causing the processor to reset. The watchdog
will also reset the processor if the power supply falls
below 4.75 VDC. These two features allow the instrument
to recover from abnormal software and hardware
conditions.
Real Time Clock (RTC): The real time clock maintains the
current date and time. The RTC uses an internal clock
circuit with an internal, 10-year life, lithium battery to
perform timekeeping. The battery also preserves the
contents of internal memory.
Dip Switch: The four-position dip switch allows the user
to download new software via one switch. The other
switches are unused at this time.
Voltages: Three voltages are present on the CPU board:
+5 VDC, +12 VDC, and VPP. +5 VDC powers all the logic.
+12 VDC is switched on and o to create the flash
memory’s programming voltage, VPP.
Glue Logic: The glue logic performs the functions of
creating the RAM memory chip selects, the Flash
memory write signals, the VPP control signal, the
watchdog control signal, and accessing the dip switch.
The CPU board has two software accessible hardware
registers to read the dip switch and to control watchdog
and VPP.
Connector: A 50-pin connector interfaces with the
application PCB.
2.4 FL2167PC Application PCB
The application PCB contains all circuits specific to the
instrument. The board includes a microprocessor, voltage
converters, precision voltage reference, signal
conditioning circuits, analog-to-digital converters,
digital-to-analog converters, programmed logic, drive
circuits, a temperature sensor, a speaker, and serial ports.
Microprocessor: The PIC18 microprocessor manages all
of the application specific hardware. The PIC18
communicates with the 80C186 processor on the
processor PCB via a parallel slave port (PSP), and acts as
the I2C master for serial communications with several ICs
on the application PCB. The PIC18 uses firmware to read
thermistor outputs on its integrated 10-bit analog-to-
digital circuits, and then regulate the instrument’s three
heaters to a set point. A fourth analog-to-digital
converter monitors the current through the system’s
exhaust fan. The PIC18 sets the state of the incubator
heater, incubator indicator LEDs, the sample illumination
LED, and the shutter solenoid.
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