24
The Advanced
®
3D3/4D3 Service Manual
I/O Ports: Circuitry for the two serial ports
(RS-232 and barcode) and the parallel printer
port, is present on the application board with
cabling to the actual connectors on the back
panel.
Display & Keypad: The display and keypad
are interfaced to the processor via program-
mable logic devices (PLDs). The keypad is
polled in a row/column process which identi-
fies the key pressed to the microprocessor.
The application logic, in response to proces-
sor commands, controls the LEDs located on
the keypad.
Light Emitting Diodes (LED): LEDs are
provided to indicate when a high current load
is active, a sensor is tripped, or a voltage sup-
ply is active. Green LEDs are used on the
power supply voltages, yellow LEDs are used
on driver signals such as the fan and head
motor controls, and red LEDs are used to
indicate that the head up and down optical
sensors have been tripped.
Application Logic: The application logic is
made up mainly of two programmable logic
devices (PLDs). These provide software
accessible hardware registers, enabling the
software to read the keypad, sensors, and ana-
log-to-digital converters. These also allow
manipulation of the display, external compo-
nents such as the fan, head motor, etc., and
interface to the RS-232 ports. The printer is
controlled directly from the microprocessor
through an 8-pin D-latch.
Connectors: Connectors are supplied for the
CPU PCB, display, keypad, power, drives,
probes, and back panel I/O ports.
Printer Power Outlet: A printer power out-
let eliminates the need for a wall transformer
with an external printer. The 3-pin DIN sock-
et, located on the back of the instrument, sup-
plies up to 1 Amp at 12 VDC via the follow-
ing connections:
Pin 1 (left) +12 VDC
Pin 2 (center) not connected
Pin 3 (right) ground
Printer Port: The printer port connector on
the back of the instrument provides 8 data
lines and the necessary handshaking signals
for communication with most standard print-
ers. The printer port connections are as fol-
lows:
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 RS-232
line driver/receiver provides the microproces-
sor 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:
Signal Pin Direction
Carrier Detect 1 to 3D3/4D3
Receive Data 2 to 3D3/4D3
Transmit Data 3 from 3D3/4D3
Data Terminal Ready 4 from 3D3/4D3
Signal Ground 5 common
Data Set Ready 6 to 3D3/4D3
Request to Send 7 from 3D3/4D3
Clear to Send 8 to 3D3/4D3
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