4
dc2227af
DEMO MANUAL DC2227A
aDDitional information
Operation in SIO Mode
The device can also operate in SIO mode. In this mode,
no IO-Link communication takes place either because the
master connected to the device is in the “Inactive” mode
and it only supplies power to the device, or because there
is no master connected to the device in which case the
device is powered by a 24V supply. In SIO mode, the
DC2227A reacts to the status of the light barrier as follows:
•
If the light barrier is open, then drivers CQ1 and Q2
actively pull low. Since the onboard light bulb is con-
nected between Q2 and ground, it is therefore turned
off.
•
If the light barrier is closed (by placing a piece of paper
in its gap), CQ1 and Q2 actively pull high and the light
bulb attached to Q2 turns on.
Temperature Sensor Configurations
In IO-Link mode, the DC2227A reports cyclically to the
master (and thus to the PC Control Tool) the temperature
measured by the on-board LTC2997. In order to measure
temperature the LTC2997 uses an NPN configured as a
diode. The NPN can be either on-chip, on PCB (Q1) or
remote. Refer to the Connectors and Jumpers section for
detailed information on how to choose the NPN.
Microcontroller ADC’s Offset Correction
The 12-bit ADC of the Atmel microcontroller samples
both, the precise 1.8V reference voltage (V
REF
) and the
VPTAT outputs of the LTC2997 to report the temperature
in Celsius to the IO-Link master. The temperature is then
calculated using a ratiometric measurement. The µC’s
ADC is specified to have offsets from –40 to 40 LSBs.
The temperature equation is:
100
•
T(
°
C)
=
ADC7 –OFFSET
ADC4–OFFSET
• 45000 – 27315
ADC7 is the ADC’s code for the VPTAT output and ADC4
the code for the precise 1.8V V
REF
. OFFSET is the ADC’s
offset (in LSB) parameter that can be set using the control
tool (default is 0 LSB). In order to improve the accuracy
of the temperature reading, a calibrated thermometer can
be used to measure the temperature close to the LTC2997
and then the ADC Offset parameter can be set to the value
(after several tries) that minimizes the error between the
temperature reported by the Control Tool and that given
by the calibrated thermometer.
Event Generator
The DC2227A is also equipped with a pushbutton to
simulate events generated by IO-Link devices to inform
IO-Link masters of requests that require special attention.
Light barrier
The light barrier offers many ways to interact with the
device. It starts the device in COM3 mode if it is closed
during power-up or in COM2 mode if left open. In IO-Link
mode, its status is reported live on the PC control tool and
in SIO mode its status is directly coupled to the CQ1 and
Q2 drivers, thus allowing the user to operate the light bulb.
Light bulb
A 28V/100mA light bulb connects between Q2 and ground
and serves to show the high current driving capability of
the line drivers. It takes about 240ms to be turned on fully
by the pulsing mechanism of the LT3669-2. To prevent data
loss in IO-Link mode, driver Q2 is only enabled in between
IO-Link telegrams. To turn it on and off from the control
tool (in COM2 only) simply press the “Turn On” and “Turn
Off” buttons within the light bulb section. In SIO mode,
regardless on the IODD file chosen, the light bulb can be
switched on and off by interacting with the light barrier.
