I/O Discrete (Module K6 Ver. 4)68C3 Operations Manual North Atlantic Industries, Inc. 12/19/2014Rev: 2014-12-19-0947 www.naii.com Page 176 of 330Current for Source/SinkProgram any current from 0 to 5 ma. Programs entire bank; there are 4 channels per bank. For 5ma, enter integer50. Resolution is 100μa per bit (LSB=100μa). A current value of zero disables the current source/sink circuitsand configures for voltage sensing.REGISTER D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 FUNCTION3.2 1.6 0.8 0.4 0.2 0.1 value in mA (LSB=100μA)CURRENT X X X X X X X X X X D D D D D D D=DATA BITExamples: Register value is integer:Register Data Bits Channel Configuration, Module 1Value D15-D2 D1 D0 Ch. 9-16 Ch. 5-8 Ch. 1-40 0000 0000 0000 00 - - 0 0 Pull-Down Pull-Down Pull-Down1 0000 0000 0000 00 - - 0 1 Pull- Down Pull-Down Pull-Up2 0000 0000 0000 00 - - 1 0 Pull- Down Pull-Up Pull-Down3 0000 0000 0000 00 - - 1 1 Pull- Down Pull-Up Pull-UpTo detect an OPEN line when contact sensing, add 10k ohm resistor Rnl nearest to load. Program open detect current Iodand calculate open contact condition, drop voltage Vopen at I/O pin. Select sourcing current Iod such that drop voltage ΔV isabout 80% of Vcc. If open detect resistance Rod is the parallel combination of the near load resistance Rnl and the circuit inputimpedance Zin. Then (example, Zin = 105K):Rod = Rnl || Zin = 10k || 105k = 9.13 k. 105 K used as example for K6 (v3)If user provided Vcc is 10v, Must RECALCULATE example for actual ZinK6 (v4) Zin = 1 MΩIod = 0.8 Vcc / Rod = 0.8 x 10 / 9.13k = 0.876 mA.If Iod = 1mA, we get open contact condition, drop voltage Vopen at the I/O pin,Vopen = IodRod = .0876 mA x 9.13 kΩ = 8.0 volts.If load is current sink, Program Maximum Upper Threshold Tmu some 20% greater than Vopen , maintainingVcc > Tmu > Vopen > TutTmu = 1.2 Vopen = 1.2 x 8 = 9.6 volts.Program Upper Threshold Tut 20% less then VopenTut = 0.8 Vopen = 0.8 x 8 = 6.4 volts.Accordingly, program Lower Threshold Tlt at 20% Vcc and Minimum Lower Threshold Tml at 10% VccTlt = 0.2 Vcc = 0.2 x 10 = 2 volts.Tml = 0.1 Vcc = 0.1 x 10 = 1 volts.To detect a line shorted to either ground or Vcc when contact sensing, continuing with this example, the user needs toadd series resistance nearest to load, Rs, and calculate closed contact condition, drop voltage Vclosed at I/O pin. Resistancenearest to load, Rs, should be negligible as compared to the near load resistance Rnl but at least a magnitude greater than anyresistance due to wire length. A value of 150 ohms would be appropriate for Rs. Then:Vclosed = IodRs = 0.876 mA x 0.15 kΩ = 0.13 volts.Program Lower Threshold Tmu greater than Vclosed maintainingVcc >> Tlt > Vclosed > Tml > 0Tlt > 1.2 Vclosed > 1.2 x 0.13 = 0.156 volts.Program Minimum Lower Threshold Tut 20% less than VopenTml < 0.8 Vclosed < 0.8 x 0.13 = 0.1 volts.
