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Reference Manual
00809-0400-4728, Rev AA
June 2011
3-5
Rosemount 644
The block supports two forms of the PID equation: Standard and Series. You
can choose the appropriate equation using the MATHFORM parameter. The
Standard ISA PID equation is the default selection.
Resource Block FEATURES and FEATURES_SEL
The parameters FEATURES and FEATURE_SEL determine optional
behavior of the 644.
FEATURES
The FEATURES parameter is read only and defines which features are
supported by the 644. Below is a list of the FEATURES the 644 supports.
UNICODE
All configurable string variables in the 644, except tag names, are octet
strings. Either ASCII or Unicode may be used. If the configuration device is
generating Unicode octet strings, you must set the Unicode option bit.
REPORTS
The 644 supports alert reports. The Reports option bit must be set in the
features bit string to use this feature. If it is not set, the host must poll for
alerts.
SOFT W LOCK
Inputs to the security and write lock functions include the software write
lock bits of the FEATURE_SEL parameter, the WRITE_LOCK parameter,
and the DEFINE_WRITE_LOCK parameter.
The WRITE_LOCK parameter prevents modification of parameters within
the device except to clear the WRITE_LOCK parameter. During this time,
the block will function normally updating inputs and outputs and executing
algorithms. When the WRITE_LOCK condition is cleared, a WRITE_ALM
alert is generated with a priority that corresponds to the WRITE_PRI
parameter.
The FEATURE_SEL parameter enables the user to select the software
write lock or no write lock capability. In order to enable the software write
lock, the SOFT_W_LOCK bit must be set in the FEATURE_SEL
parameter. Once this bit is set, the WRITE_LOCK parameter may be set to
“Locked” or “Unlocked.” Once the WRITE_LOCK parameter is set to
“Locked” by the software, all user requested writes as determined by the
DEFINE_WRITE_LOCK parameter shall be rejected.
The DEFINE_WRITE_LOCK parameter allows the user to configure
whether the write lock function will control writing to all blocks, or only to
the resource and transducer blocks. Internally updated data such as
process variables and diagnostics will not be restricted.
N/A = No blocks are blocked
Physical = Locks resource and transducer block
Everything = Locks every block.