Rockwell Automation PLC-5 Fieldbus Solutions for Integrated Architecture User Manual - Manual (Page 165)

Publication 1757-UM006A-EN-P - May 2002
Using the 1788-CN2FF, ControlNet-to-FOUNDATION Fieldbus H1 Linking Device 7-5
and Confirmed after the condition causing the alarm is corrected.
When the function block detects the alarm condition is no longer
present, the alarm is said to be CLEARED. The CLEARED state must be
Confirmed when it is detected. Users of the LD use the alarm
attributes to process Fieldbus alarms.
Each attribute corresponding to a process alarm has the three
alarm-related bits as shown in Figure 7.3.
Figure 7.3 Alarm Attribute Definition
Bits 7-3, DON’T CARE, are undefined when read and should be
ignored when performing a GET. The DON’T CARE bits should be
written as 0 when performing a SET. Bit 2, Acknowledge, is undefined
when read and should be ignored when performing a GET. When a
user wants to Acknowledge an alarm, this bit should be written as a 1
when performing a SET. Each time the LD detects a 1 in the
Acknowledge position, a Fieldbus Acknowledge will be generated.
Therefore, users must be careful not to set the Acknowledge bit more
than once per alarm. Bits 1 and 0, CLEARED and ACTIVE respectively,
are read/write bits.
When an alarm condition is ACTIVE or CLEARED, these bits are read
as a 1 when performing a GET. The user must Confirm each of these
states by writing them to a 0 by a SET. Once an alarm has occurred
(become ACTIVE), alarm processing is NOT complete until the user
intervenes to remove the alarm condition, Acknowledges the alarm
(writing a 1 in the Acknowledge bit position), Confirms the alarm
(writing a 0 to the ACTIVE bit position once it is read as a 1), and
Confirms the alarm condition being CLEARED (writing a 0 to the
CLEARED bit position once it is read as a 1)
Analog Outputs This section describes configuration of the linking device to control
any analog value (and status) in a Fieldbus device, such as in a Analog
Output (AO) function block. It also describes the attributes of the
created ControlNet analog output object.
The linking device contains two of MAO block instances on each
Fieldbus channels. Each instance of the MAO block is the software
equivalent of an analog output module in an I/O subsystem. Each
MAO block also has eight channels or outputs, with each channel
containing a float and a status pair. Each MAO block has eight inputs
to provide for the BKCAL or readback from the analog output function
Bit Position
Value Acknowledge CLEARED ACTIVE
0 1 2 3 4 5 7 6
X X X X X