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2–4
Preliminary Adjustments
Binary/BCD Data Format
1771 IJ
Publication 1771 UM006B-EN-P - June 2002
Binary/BCD data format (switch 5) - The preset values and the
accumulated total in the status word have the option of appearing in
either BCD or binary formats. If the BCD format is selected, the
processor can directly manipulate these values in comparisons or
arithmetic functions but the accumulated value is limited to a count
between 000 and 999. The binary option allows an increased range
of 0000 to 4095
. With some processors, the programming must
10
reconstruct a BCD number from the binary value. To select binary
mode, set switch 5 on. To select BCD mode, set switch 5 off.
Because different types of input devices are compatible with
different voltage ranges, the 1771-IJ (5V dc) and 1771-IK (12-24V
dc) input channels are configured differently.
Because the 1771-IJ module is designed to work with 5V TTL type
devices, each input channel and the marker input can be set for
single ended or differential line inputs (Table 2.C). The input device
should be capable of providing 16mA of sink current. The module
detects a voltage of 2.4V dc or above at either channel as logic "1"
or true. A voltage below 0.6V dc is considered as logic "0" or false.
Table 2.C
Input Configuration Switch Assembly 1771 IJ SW 2
1
Marker
On
Single ended
Off
Differential
The marker input registers as true when the input pulse from the
encoder is high.
The limit switch input senses a voltage of greater than 10 volts dc as
logic "1" (on), and less than 5 volts dc as logic "0" (off). The input
voltage that appears through the switch should be from a 12 to 48V
dc external supply capable of supplying 10mA of source current at
48V dc. The limit switch input has a signal delay of 16ms (+7ms)
because of the filtering needed to protect against contact bounce.
The channel B input can be used in the counter mode to select count
direction. If the channel B input terminal is not connected, the
control word in the output program selects the direction of the count.
For external hardware control, the count direction bit in the control
word must be set to count up.
Then if channel B is allowed to float high or is driven high, the
module counts up; if it is pulled low, either through a gate or a
transistor switch, it will count down.
2
3
Chan. B
Chan. A
Single ended
Single ended
Differential
Differential
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