28
The Advanced
®
3D3/4D3 Service Manual
General: The microprocessor is an 8 bit
Hitachi 63A03R (a member of the 6800 fami-
ly of microprocessors). The microprocessor
runs at approximately 1 MHz and has an
address space of 64 kBytes. The micro-
processor runs the software stored in
48 kByte of EPROM and uses the battery-
backed-up 8 kByte static RAM to store infor-
mation.
A/D Converters: Two dual-slope A/D con-
verters using programmable timer modules
provide interface from the sample and block
probes to the microprocessor. The A/D con-
verters use a reference voltage of 6.25 VDC
and provide 15 bits (1/4 ohm) of resolution.
Front End Interface: The thermoelectrics
are interfaced to a programmable timer mod-
ule through discrete logic. The programmable
timer module interfaces directly to the micro-
processor. The stir/freeze wire is interfaced to
the D/A converter through discrete logic.
The power transistors, mounted either on the
back of the instrument or underneath the
power supply, control the thermoelectrics and
the stir/freeze wire. The fan is interfaced to
the microprocessor through discrete logic.
D/A Converter: The D/A converter uses a
60 Hz 0-5 volt reference from a programma-
ble timer module through discrete logic. The
D/A converter interfaces directly to the micro-
processor.
Head Motor Interface: The AC motor run-
ning at 120 VAC controls the head (which
contains the sample probe and the stir/freeze
wire). Two relays mounted to the back of the
instrument control the voltage to the AC
motor. These relays interface to a peripheral
interface adapter through discrete logic. The
peripheral interface adapter interfaces directly
to the microprocessor. Two optical sensors
(see the head sensor board below) detect the
head up and head down positions.
Keypad Interface: A peripheral interface
adapter is used to interface the keypad,
through the keypad transition board (see
below), to the microprocessor. A 3 to 8 line
decoder is used to pulse the different columns
of the keypad to check for key presses. The
microprocessor controls the keypad LEDs.
Display and Port Interfaces: A peripheral
interface adapter is used to interface both the
display and the printer port to the micro-
processor. A printer power outlet (see below)
eliminates the need for a wall transformer
with an external printer.
The printer port connector on the back of the
instrument provides 8 data lines and the nec-
essary handshaking signals for communica-
tion with most standard printers. The printer
port connections are as follows:
Pin-Out
Signal Port Connector Cable Output
Strobe 81
Data 0 22
Data 1 33
Data 2 44
Data 3 55
Data 4 66
Data 5 14 7
Data 6 78
Data 7 15 9
Ready 1 11
Ret. Gnd 9 19
Ret. Gnd 10 20
Ret. Gnd 11 21
Ret. Gnd 12 22
Ret. Gnd 13 23
Serial (RS-232) Port Interface: An asyn-
chronous Communications Interface Adapter
and RS-232 line drivers/receivers provide the
microprocessor with a serial port interface
that supports both hardware and software
handshaking.
The DB-9 RS-232 port conforms to the DTE
RS-232C standard and has the following pin
assignments:
To Next Page
Loading...
