
UM-0085-B09
DT80 Range User Manual
Page 332
RG
Digital Inputs
The DT80’s 8 digital I/O terminals (4 for DT81/82E) can be read individually, or can be read as 4 or 8 bit words.
The following channel types are used to read the states of digital inputs:
Channel Type
Valid Channel Numbers Description
DS
1
-
8
(DT80/85)
1
-
4
(DT81/82)
Digital State
: returns the state of digital input; 0=low, 1=high
DN
1
-
5
(DT80/85)
1
(DT81/82)
Digital Nybble
: returns the state of four consecutive digital inputs starting at the specified
input as a 4-bit number (0-15). The specified input will form the least significant bit of the
result.
DB
1
Digital Byte
: returns the state of all eight digital inputs as an 8-bit number (0-255). Input
1D
is the least significant bit.
For example, if channel
3DN
returns the value 13 (binary 1101) then this indicates that input
3D
(lsb) is high,
4D
is low,
5D
is high and
6D
(msb) is high
Channel Options
The following channel options are applicable to digital input channel types:
•
channel factor: for the multi-bit channel types (
DN
,
DB
), the channel factor is a bitmask which specifies which
digital inputs to read. The default values for
DN
and
DB
are 15 and 255 respectively (i.e. read all bits)
For example,
2DN(7)
(bitmask = 0111 binary) will return the state of inputs
2D
,
3D
and
4D
in bits 0 (lsb), 1 and 2
respectively. For input 5D the mask bit is zero so it is not read and bit 3 (msb) of the returned value will always be zero.
5D can then be used as an output if desired, e.g.
2DN(7)
simultaneously read inputs
2D
,
3D
,
4D
5DSO=1
drive
5D
as an output
Connecting to Digital Inputs
The two groups of digital input channels have different electrical characteristics. In particular:
•
Inputs
1D-4D
(
1D-3D
for DT81/82E) include a 47k pull-up resistor. The default state (if nothing is connected) is
therefore high. This in turn means that channels
1..4DS
will return 1 if the inputs are not connected.
•
Inputs
5D-8D
(
4D
for DT81/82E, none for DT82I) include a 200k pull-down resistor. Their default state is
therefore low (0). So if all 8 inputs are disconnected then
1DB
will return 15 (00001111).
Warning:
The DT80’s digital inputs are not reverse-polarity-protected. Therefore ensure signal polarity is correct — positive to
numbered terminals, negative to
DGND
terminals — before connecting signals to the DT80’s digital inputs.
Do not apply more than 30Vdc to inputs
1D-4D
(
1D-3D
for DT81/82E), and do not apply more than 20Vdc to inputs
5D-8D
(
4D
for DT81/82E).
DI1 – Relay Inputs
Voltage-free relay contact closures can easily be detected on channels
1D-4D
(
1D-3D
for DT81/82E) by wiring the relay
contacts between the input pin and
DGND
, as shown below.
Channels
5D-8D
(
4D
for DT81/82E) are less suitable for relay contact inputs, but they can still be used, for example if the
contacts are wired between the input pin and an external 3-20V dc supply (or one of the DT85/DT80 Series 2-4’s power
outputs,
12V
or
PWR OUT
).
Figure 155: Wiring for reading contact closures on digital inputs
To measure
Use the command
state
1DS
(0 = contacts closed, 1 = contacts open)
Содержание DT80
Страница 29: ...UM 0085 B09 DT80 Range User Manual Page 29 RG The DT80 File System P114 ...
Страница 184: ...UM 0085 B09 DT80 Range User Manual Page 184 RG Figure 71 DT80 communications options ...
Страница 185: ...UM 0085 B09 DT80 Range User Manual Page 185 RG Figure 72 DT80 communications options integrated modem models ...