SMAR FRI303, Instruction Manual

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Section 2
2.1
OPERATION
The FRI303 has 2 isolated built-in relay outputs and two dry contact inputs. It is therefore ideal for
interfacing existing discrete devices to a Profibus-PA system.
Output function blocks include standard Profibus-PA safety mechanisms in case of failures. Outputs
are isolated from each other.
NOTE
For each output there is a 250mA protection fuse. To access them, please, remove the main electronic board
and in the Relay board see the reference FU1 and FU2. The code for them is LIT 251.250 – 0.250 A – from
LittelFuse.
Functional Description – Electronics
Refer to the block diagram (See Figure 2.1 – FRI303 Block Diagram). The function of each block is
described below.
(CPU) Central Processing Unit, RAM and FLASH
The CPU is the intelligent portion of the Profibus-PA Relay and dry contact Input, being responsible
for the management and operation of block execution, self-diagnostics and communication. The
program is stored in Flash memory. For temporary storage of data there is a RAM. The data in the
RAM is lost if the power is switched off. However, the device also has a nonvolatile EEPROM where
data that must be retained are stored. Examples of such data are configuration and identification
data.
Communication Controller
It monitors line activity, modulates and demodulates the signal from the network.
Power Supply
Takes power of the loop-line to power the converter circuitry.
Display Controller
Receives data from the CPU and drives the Liquid Crystal Display.
Input Latches
Store the information of the inputs' conditions.
Output Latches
Store the information of the outputs' conditions.
Local Adjustment
There are two switches that are magnetically activated. They can be activated by the magnetic tool
without mechanical or electrical contact.
Optical Isolation
Optical isolation is for outputs and inputs.