Maple Systems OIT Family - Manual (Page 26)

Sample Status Coil Addresses
GE Fanuc
%M# Address
Allen-Bradley PLC-5
B3:0 Address Status Coil
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
B3:0/0
B3:0/1
B3:0/2
B3:0/3
B3:0/4
B3:0/5
B3:0/6
B3:0/7
B3:0/8
B3:0/9
B3:0/10
B3:0/11
B3:0/12
B3:0/13
B3:0/14
B3:0/15
Message Received bit
Invalid Display Message Number bit
Message/Keytable Error bit
Reset bit
Alarm Stack Full bit
Message Stack Full bit
Message Stack Empty bit
Clear Alarm bit
Clear Alarm Stack bit
OIT Pulse bit
Update PLC Clock bit
Alarm Stack Empty bit
Acknowledge Alarm bit
Reserved for future use
Reserved for future use
Reserved for future use
Message Received
The Message Received status coil is set by the OIT when a screen request has been
successfully retrieved from the PLC. Therefore, it can be used by both the OIT and the
PLC to perform handshaking when new screens are requested. For proper handshaking,
the PLC should monitor this coil to determine if the last screen request sent to the OIT
has been read. Additional screen requests should not be sent to the OIT until this coil has
been set. It is the PLC’s responsibility to clear this coil before sending another screen
request to the OIT. For more information on the message request sequence, refer to the
Message Request Register section in this chapter.
NOTE:The PLC can ignore this coil if the OIT’s polling rate of the message request register
(200 milliseconds) is faster than the PLC’s message update rate.
Invalid Display Message Number
The Invalid Display Message Number status coil is set by the OIT when the PLC requests a
non-existent or empty screen. In systems designed for high integrity, the PLC should clear the
coil, then activate an error coil indicating to the outside world that a problem exists so that the
system programmer can correct the programming error either in the PLC or in the OIT.
Message/Keytable Error
The Message/Keytable Error status coil is set by the OIT when it detects invalid or
corrupted data in the screens or keytable. For instance, this coil is set if a function key is
pressed that has been configured to display a screen that does not exist. This coil is also
set by the OIT when it detects that the message or function key databases have been
contaminated. Since all of the configuration data is stored in FLASH EPROM, this error
should never occur. However, in the event of a component failure, this coil indicates that
an error has been detected in the OIT.
Operational Overview 26
1010-0099, Rev. 07