Service Information
4-2
3. Place the mainframe in the “read input channels” dis-
play mode by selecting the READ-I/O-CARD option of
the CARD COFIGURATION MENU. Verify on the dis-
play that the input channel is off (open).
4. On the mainframe, press OPEN ALL to turn off (open)
the output channel and verify on the display that the in-
put channel turns on (closes).
5. On the mainframe, use the EXIT key to return the instru-
ment to the normal display mode and verify on the dis-
play that the output channel is off (open).
4.4
Static-sensitive devices
CMOS and other high-impedance devices are subject to pos-
sible static discharge damage because of the high-impedance
levels involved. When handling such devices, use the precau-
tions listed below.
In order to prevent damage, assume that all parts are static-
sensitive.
1. Such devices should be transported and handled only in
containers specially designed to prevent or dissipate
static build-up. Typically, these devices will be received
in anti-static containers made of plastic or foam. Keep
these parts in their original containers until ready for in-
stallation or use.
2. Remove the devices from their protective containers
only at a properly-grounded workstation. Also, ground
yourself with an appropriate wrist strap while working
with these devices.
3. Handle the devices only by the body; do not touch the
pins or terminals.
4. Any printed circuit board into which the device is to be
inserted must first be grounded to the bench or table
5. Use only anti-static type de-soldering tools and
grounded-tip soldering irons.
4.5
Principles of operation
The following paragraphs discuss the basic operating princi-
ples for the Model 7020, and can be used as an aid in trou-
bleshooting the card. The schematic drawing of the Scanner
card is shown on drawing number 7020-106, located at the
end of this Section 5.
4.6
Block diagram
Figure 4-2 shows a simplified block diagram of the
Model 7020. Key elements include the output channel driv-
ers and the input channel registers, as well as the ROM,
which contains card ID and configuration information. These
various elements are discussed in the following paragraphs.
4.7
ID data circuits
Upon power-up, card identification information from each
card is read by the mainframe. This ID data includes such in-
formation as card ID, settling time, and channel configura
tion information. ID data is contained within an on-card
EEPROM (U107). In order to read this information, the se-
quence described below is performed on power-up.
OUTPUT CHANNEL
INTERNAL CONNECTIONS:
INTERNAL VOLTAGE SOURCE (5.3V) SELECTED.
PULL-UP RESISTOR INSTALLED.
OUT
GND
INPUT CHANNEL
IN
GND
Figure 4-1
Testing an input or output channel
Figure 4-2
Model 7020 block diagram
OUT DATA
OUT CLOCK
STROBE
ENABLE
OUTPUT
CHANNEL
DRIVERS
U109 –
U113
OUT 1
OUT 2
OUT 40
FROM
MAINFRAME
IN DATA
IN CLOCK
STROBE
ENABLE
INPUT
CHANNEL
REGISTERS
U100 –
U104
IN 1
IN 2
IN 40
TO
MAINFRAME
ID CLK
ID DATA
ROM
U107
TO/FROM
MAINFRAME
FROM
MAINFRAME