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KB82420
Unexpected count value read from SNAP-SCM-SSI
Revision:  2.0
Published:  4/1/2013
Applies To
Firmware for:
SNAP-PAC-EB1
SNAP-PAC-EB2
SNAP-PAC-EB1-W
SNAP-PAC-EB2-W
SNAP-PAC-SB1
SNAP-PAC-SB2
Versions
Problem was discovered in version:  
R9.2c
Problem is fixed in version:  
R9.3b

SYMPTOMS

The count values read from a SNAP-SCM-SSI module by a SNAP PAC brain may be outside of the expected count range based on the type of encoder used in an application.

Example:

A 14-bit encoder should return count values from 0 to 16383 counts when read by a SNAP PAC brain and a SNAP-SCM-SSI module. Instead, count values of 0 - 16777215 are returned.

WORKAROUND

With the PAC Control Strategy running, from PAC Control or PAC Manager, divide the counts returned for the SNAP-SCM-SSI input point by the difference of the Data Bits in Data Frame field from 24.

Example: A 14-bit encoder is used with no error bits in the data frame. When configuring the SNAP-SCM-SSI module in PAC Manager, enter 14 in the Data Bits in Data Frame field.

With the returned value from PAC Manager or PAC Control, calculate the correct counts with this formula:

Corrected Counts = Counts / (24 bits - 14 bits)

Where Counts is the count value seen in PAC Manager or PAC Control.

CASE STATUS

Opto 22 has resolved this issue.

Relevant Downloads
No relevant downloads have been specified.
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