User’s Manual
DM5856HR/DM6856HR
18 RTD Finland Oy
Isolated digital outputs
The Isolated input stage of the DM5856HR/DM6856HR consists of two major parts:
1. Optocouplers
2. Output registers
1. Optocouplers
Small SMD-optocouplers are used to isolate each channel of the isolated outputs. Individual
optocouplers are used for each channel. The optocouplers are directly connected to the Output
latch. The output optocoupler transistor is in the open collector configuration with a pull-up resistor,
which is connected to the collector. A 4,7 KOhm resistor is used as a pull-up to the supply. The
output 4.7 Kohm pull-up resistor has been installed for a +5 - 30V isolated output range.
2. Output registers
The optocouplers are connected to two 8-bit data registers, which are directly addressable with a
write operation at address BASE+0 and BASE+1. The state of the outputs does not change even
though a system reset may occur. A write to the output latch will update the state of the outputs.
