160    HC900 Process & Safety Controller User and Installation Manual  Revision 6 
    21 April 2017 
Table 22 – Controller Operating Modes 
Functions in selected mode 
I/O scanning (Controller and Expander Racks) 
Function block execution; outputs are set according to function block algorithms. 
Monitoring of Diagnostics (controller rack and I/O expander racks) 
Detection of I/O Modules 
Other functions permitted: 
  Downloading of configurations 
  Indications of Forces at Status LEDs on I/O modules 
Other functions NOT permitted: 
  AI calibration 
  AO calibration 
I/O scanning (Controller and expansion Racks is performed, but function blocks are 
not executed, and all outputs (digital and analog) are set to OFF.  (See Note 1.) 
Monitoring of Diagnostics (Controller and Expander Racks) 
Detection of I/O Modules 
Other functions permitted: 
  AI calibration 
  AO calibration 
  Downloading of configurations 
  Downloading controller firmware (Program Locked or Program) 
Other functions NOT permitted: 
  Indications of Forces at Status LEDs at I/O modules 
IO scanning (Controller and Expander Racks) is performed, but function blocks are 
not executed, and all outputs (digital and analog) are Frozen (see Note 2) at the 
states they were in when the OFFLINE mode was selected. 
Monitoring of Diagnostics (local and expanded racks) 
Detection of I/O Modules 
Other functions permitted: 
  AI calibration 
  Indications of Force at Status LEDs of I/O modules 
Other function NOT permitted: AO calibration 
Note 1: The Off state of the module outputs are defined as: 
  Digital output - low state 
  Time proportional Output (TPO) : 0% duty cycle 
  PPO and TPSC Outputs: Both Fwd and Rev are Off. 
  Analog output: 0.0 mA 
Note 2: The Frozen states of module outputs are defined as: 
  Digital output: same state as previous (last active state) 
  Time Proportional Output (TPO): Same duty cycle as in last active state  
  PPO and TPSC Outputs: digital outputs are Off to freeze the motor position. 
  Analog output: same current as previous (last active current level)