Service manual

PN 4237242C
2.6-1
INSTRUMENT DESCRIPTION
PERIPHERALS
2
2.6 PERIPHERALS
Floppy Disk Drive
The floppy disk drive is a standard 3.5 in., 1.44 MB, Double-sided High-density drive. The
main system program is loaded from this drive on power up or reboot. A program disk is used
to power up the instrument, but a calibration or control disk may be requested. Software
updates merely require that the new program disk be used at power ON.
Display
Visual output is provided by a 4-row by 40-column, character only LCD. This display
(Figure 2.2-1) has an operating temperature range of 0 to 50°C. Electrical input consists of
one 16-pin connector, connected through a ribbon cable to the URA card. Pins 1 through 8
are the data bus, pins 9 through 12 are the control lines, pin 13, V
0
,
is the display contrast
voltage, pin 14, V
DD
,
is the +5 Vdc power supply, and pins 15 and 16 are the ground pins.
The display is a component piece purchased from an outside vendor, so low-level
troubleshooting is not an option.
Keypad
The MD II keypad (Figure 2.2-1) is a 36-switch, non-tactile, membrane keypad with a
graphic overlay. The MD II makes use of only 24 switches. All switches are environmentally
sealed with an operating temperature range of +10 to +35°C. Switch selection uses a standard
row/column matrix methodology, output through a 20-pin flex ribbon cable to the URA card.
A separate flex cable for the built-in electrostatic shield is connected to the chassis for
grounding.
Both cables are part of the component as purchased and
cannot
be changed separately.
Rear Panel Interface Connectors
There are three interface connectors on the rear panel, Serial 1, Serial 2 and the Parallel
Printer connector (Figure 3.2-2). All three connectors attach directly to the AT motherboard.
Serial 1 is a 25-pin, RS-232 serial connector and Serial 2 is a 9-pin, RS-232 serial connector.
Serial 1 is used for the ASTM host interface while Serial 2 is unused. The Parallel Printer
connector is a standard Centronics 25-pin output connector that is used for the system
Printer. Pinouts for the serial ports are shown in Table 2.6-1.
Table 2.6-1 Pinouts for Serial Ports
Function Direction Serial 1 (25 Pin) Serial 2 (9 Pin)
No Connection N/A 1 (shield) N/A
Transmitted Data From MD II 2 3
Received Data To MD II 3 2
Request To Send From MD II 4 7
Clear To Send To MD II 5 8
Data Set Ready To MD II 6 6
Signal Ground N/A 7 5
Data Terminal Ready From MD II 20 4
Ring Indicator To MD II 22 9
C