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94
Application Notes
Table 14: Pin Assignment
Pin
Signal
Pin 1
RXTX+
Pin 2
Shield
Pin 3
RXTX-
Pin 4
Trigger
Pin 5
Attention
Pin 6
V+
Pin 7
V+
Pin 8
GND
Pin 9
GND
The Parallel Interface
The 25-pin D-subminiature connector is used for the parallel interface.
The pin assignment for the parallel interface is outlined in Figure 23 and Table 15.
Description
Transmit/receive data positive
side (B)
Signal shield
Transmit/receive data negative
side (A)
Active low trigger signal, transis-
tor-to-transistor logic (TTL), multi-
ended, pulled UP at slave with
100 K
Active low attention signal, open
collector, pulled UP at master
with 470 ohm
5 V supplies in
5 V supplies in
Power ground
Power ground
Figure 23: Pin Assignment
Functionality
TXA. Differential input/output signal from the
RS485 host.
This line is connected to chassis ground at the
host end and is isolated at the slave.
The two data lines are run as a twisted pair.
The Power and Ground lines are run as
twisted pair. The shield is used to encase both
of the twisted pairs within the cable.
TXB. Complement of the differential input/out-
put from the RS485 interface.
This line is driven by the host processor (mas-
ter) to indicate to the slaves that a trigger-
based action is to be executed on the falling
edge of this signal. This action is usually pre-
conditioned by a request to the applicable
slaves.
This line is driven by the SKB module (slave)
to indicate to the master that it requires the
host attention. The master is expected to poll
the slaves to determine which slave requires
attention. This signal is an open collector sig-
nal that is terminated at the host end by a 470
ohm resistor connected to Vcc.
5 V ±5% (1 to 2.5 A maximum, configuration
dependent)
5 V ±5% (1 to 2.5 A maximum, configuration
dependent)
These lines are connected to the power supply
ground, not to the chassis ground.
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