turck DeviceNet RM-89, User Manual

12 

www.turck.com

 • 1-800-544-7769 • Fax: 

(763) 

553-0708 • TURCK 

 • Minneapolis, 

MN 

55441 

www.turck.com

 • 1-800-544-7769

•  Fax: (763) 553-0708

•  TURCK  •  Minneapolis, MN 55441 

 13

TURCK 
RM-89

Programmable Parameters (continued)

Device Type

You can program how the RM-89 defines itself to the DeviceNet controller .  This parameter has a double integer (32 bit) data 

type and two fixed values .

   •

0x22

 = Resolver Device (factory default value)

   •

0x00

 = Generic Device

Non-Volatile Memory 

The RM-89 has Flash memory available to store parameter values and the position offset that results from a Preset Position 

operation .  These values are not automatically stored to flash when they are changed .  You must issue a separate “Save to 

Flash” command to store these values .

Note:

The Flash memory in the RM-89 is guaranteed for 10,000 write cycles .  Exceeding this limit will eventually lead to failure of 

the memory and the RM-89 will no longer function properly .

This limit will not be an issue for most applications .  Parameter values are rarely, if ever, changed once the machine is installed 

and commissioned .  For those applications that often change parameter values, these values can be written down to the 

RM-89 as part of the machine’s power up sequence and never stored to Flash memory .

Saving the Position Offset Value

When the position is preset with a Preset Position command, the RM-89 calculates an internal offset that is used to bring the 

reported position to the programmed Preset Value .  This internal offset is not stored in Flash memory and will be lost when 

power is removed from the unit .

•If part of the machine’s power up sequence is homing the position, then the machine’s design as-sumes the  

 position is incorrect on power up .  Therefore, there is no reason to store the internal offset to Flash memory .

•Absolute position applications will usually preset the position during machine installation and   

commissioning .  The “Save to Flash” command is then issued once to store the internal offset .  As long as   

there is no mechanical slippage in the machine, the position will always remain correct . 

Some applications require the position to be preset multiple times while the machine is running and the last internal offset 

must be stored to non-volatile memory as part of the machine’s power down sequence .  If your application falls into this 

category, you have two options:

1) When you need to preset the position value from the RM-89, calculate and store the required offset in  

    your host controller .  You will never issue a “Preset Position” command to the RM-89 . 

2) Set the 

Total Measurement Range

 parameter to a non-zero value .  When this parameter is non-zero, the  

     RM-89 constantly updates and stores the internal offset in a FRAM memory .  This includes storing the

     internal offset when a “Preset Position:” command is issued .  FRAM is a new memory technology that is  

     non-volatile, but can be written to like RAM .  (According to the manufacturer’s specifications, writing to  

     the memory every millisecond will burn out the memory in approximately 300 years .)  

     If you decide to use the 

Total Measurement Range

 parameter only to make sure the internal offset is    

     automatically stored in non-volatile memory, set this parameter to its maximum value so the

     RM-89 remains an absolute sensor .

  •When 

the 

Scaling Function Control

 parameter is disabled, set the Total Measurement Range parameter to  

  65,536 multiplied by the number of turns the RM-89 can encode . (65,536 or 268, 435, 456 counts)

  •When 

the 

Scaling Function Control

 parameter is enabled, set the Total Measurement Range parameter to  

 the value of the 

Counts per Turn

 parameter multiplied by the number of turns the RM-89 can encode .