Honeywell Increases Analog/Loop Processing Speed on HC900 Process and Safety Controller

Written by: Dan Weise

Good news!  Recent upgrades to Honeywell’s HC900 Process and Safety Controller includes a major update to analog/loop processing speeds. Even though analog/loop cycle time has been 500mS since the early 2000s, early versions of the HC900 controller were only capable of a processing speed of 2x/second.

The upgrade to the HC900 CPU’s microprocessor hardware and an associated firmware update broke that processing speed limit for their SIL-rated CPUs. Honeywell C50S and C70S model CPUs v6.1 will now process analog inputs and loops at a rate of 10x/second (100mS per update). If your process needs additional analog/loop throughput speed, you will benefit from these enhancements to the HC900 systems.

To run at 100mS, a qualified hardware configuration is required:

  • C50S or C70S SIL CPU v6.0 (with the orange faceplate)
  • High level analog input cards only, universal cards will not run at the increased speed
  • A maximum of 4 high level analog input (AI) cards per rack
  • A maximum of 2 racks (one SIL CPU, one SIL scanner)
  • No more than 500 I/O points
  • No more than 1500 function blocks

SIL CPUs can run either process logic OR safety logic, depending on the worksheet selected by the programmer in Control Designer, Honeywell’s HC900 development software.

Note: SIL CPUs are NOT required for running safety logic, as it uses only a fraction of the available function blocks.

Original release SIL CPU version 6.000 can be updated to the V6.100 functionality by loading these firmware update from the Honeywell website:

This is the current version as of April 1, 2016. For other documentation, see the Honeywell HC900 Process and Safety Controller page.


HC900 Firmware Update

Note: HC900 V4 series CPUs can not be updated for the higher processing speed.

Questions? Call (800) 953-7626


Lesman Instrument Company is the authorized Honeywell stocking distributor in North and Central Illinois, Northern Indiana, Eastern Iowa, Wisconsin, and Michigan’s Upper Peninsula. If you are located outside that area, you can find your local sales office or get technical assistance by visiting Honeywell’s contact page.


Dan Weise, Lesman Product SpecialistDan Weise, Lesman product specialist, is an instructor for training classes on process instrumentation hardware, software, and technology.

Dan has been involved in all facets of data acquisition and process instrumentation since 1978, from sales and commissioning to service and support. He’s a long-time member of ISA, and has been with Lesman since 1988.

In his words, Dan’s the guy “who reads all the manuals nobody else reads”. In Lesman customers’ words, he’s the trainer to call if you want to “cut to the SO WHAT of instrumentation”, so it’s easy to understand.

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