Emerson manual Max Notify, Rosemount 848L, Reference Manual

Reference Manual

00809-0100-4696, Rev AA September 2004

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						WRITE_LOCK		Write access
HW_SEL bit	SW_SEL bit		SECURITY SWITCH		WRITE_LOCK		Read/Write	DEFINE_WRITE_LOCK	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.

MAX_NOTIFY

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.

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.

3-5