Filter
Top Products
Reference Manual
00809-0100-4696, Rev AA
September 2004
3-5
Rosemount 848L
SOFT WRITE LOCK and HARD WRITE 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.
The following table displays all possible configurations of the WRITE_LOCK
parameter.
FEATURE_SEL
FEATURE_SEL is used to turn on any of the supported features. The default
setting of the Rosemount 848L does not select any of these features. Choose
one of the supported features if any.
MAX_NOTIFY The MAX_NOTIFY parameter value is the maximum number of alert reports
that the resource can have sent without getting a confirmation, corresponding
to the amount of buffer space available for alert messages. The number can
be set lower, to control alert flooding, by adjusting the LIM_NOTIFY
parameter value. If LIM_NOTIFY is set to zero, then no alerts are reported.
FEATURE_SEL
HW_SEL bit
FEATURE_SEL
SW_SEL bit
SECURITY SWITCH WRITE_LOCK
WRITE_LOCK
Read/Write
DEFINE_WRITE_LOCK
Write access
to blocks
0 (off) 0 (off) NA 1 (unlocked) Read only NA All
0 (off) 1 (on) NA 1 (unlocked) Read/Write NA All
0 (off) 1 (on) NA 2 (locked) Read/Write Physical Function
Blocks only
0 (off) 1 (on) NA 2 (locked) Read/Write Everything None
1 (on) 0 (off)
(1)
0 (unlocked) 1 (unlocked) Read only NA All
1 (on) 0 (off) 1 (locked) 2 (locked) Read only Physical Function
Blocks only
1 (on) 0 (off) 1 (locked) 2 (locked) Read only Everything None
(1) The hardware and software write lock select bits are mutually exclusive and the hardware select has the highest priority. When the HW_SEL bit if set to 1
(on), the SW_SEL bit is automatically set to 0 (off) and is read only.