Emerson 8700 Series, Reference Manual

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Reference Manual
00809-0100-4793, Rev CA
August 2004
Rosemount 8742C
4-8
RESOURCE BLOCK
FEATURES and
FEATURES_SEL
The parameters FEATURES and FEATURE_SEL determine optional
behavior of the Rosemount 8742C.
FEATURES
The FEATURES parameter is read only and defines which features are
supported by the Rosemount 8742C. Below is a list of the FEATURES the
Rosemount 8742C supports.
UNICODE
All configurable string variables in the Rosemount 8742C, 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 Rosemount 8742C 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 and HARD W LOCK
Inputs to the security and write lock functions include the hardware security
switch, the hardware and 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 a hardware or
software write lock or no write lock capability. To enable the hardware security
function, enable the HW_SEL bit in the FEATURE_SEL parameter. When this
bit has been enabled the WRITE_LOCK parameter becomes read only and
will reflect the state of the hardware switch. In order to enable the software
write lock, the SW_SEL bit must be set in the FEATURE_SEL parameter.
Once this bit is set, the WRITE_LOCK parameter may be set to “Locked” or
“Not Locked.” Once the WRITE_LOCK parameter is set to “Locked” by either
the software or the hardware lock, 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 functions (both software and hardware) 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 by the
security switch.
Table 4-1 displays all possible configurations of the WRITE_LOCK parameter.